Germ cell tumors of the mediastinum and testis: a comparative immunohistochemical study of 120 cases

An immunohistochemical study was performed in 120 cases of mediastinal and testicular germ cell tumors from archival, paraffin-embedded material to compare the patterns of expression between the two groups with a panel of markers, including broad-spectrum keratin, CAM 5.2 low-molecular-weight cytokeratin, placental-like alkaline phosphatase (PLAP), alpha-fetoprotein (AFP), human beta-chorionic gonadotropin (hCG), vimentin, and CD30 (Ki-1 antigen). Significant differences were observed between mediastinal and testicular seminomas: mediastinal seminomas showed strong dot-like paranuclear positivity of the tumor cells with antibodies to CAM 5.2 low-molecular-weight keratin in 80% of cases (32 of 40), as compared with only 20% positivity (5 of 24) in testicular seminomas; placental alkaline phosphatase (PLAP) was also found to be less commonly expressed in testicular seminomas (12 of 24) than in mediastinal seminomas (37 of 40); a similar pattern of expression was also observed for vimentin, which was present in scattered tumor cells in a higher proportion of mediastinal seminomas (28 of 40) than in testicular seminomas (11 of 24). The staining pattern and distribution of these markers did not show significant differences between the two groups for the various other tumor categories studied, including yolk sac tumor, embryonal carcinoma, and choriocarcinoma. The tumor cells in both testicular and mediastinal embryonal carcinoma showed strong positivity for the CD30 antigen; however, strong positivity for this marker was also observed in 6 of 25 yolk sac tumors and in scattered individual tumor cells in 4 of 63 seminomas. The results of this study show that significant differences exist between the immunostaining patterns of mediastinal and testicular seminomas, suggesting that the former may be characterized by a more mature phenotype than their testicular counterparts. Also, CD30 expression may not be necessarily restricted to embryonal carcinomas and occasionally may be observed in yolk sac tumors and seminoma cells, supporting the close histogenetic relationship that exists among these tumor types.

Expression of bcl-2 oncoprotein in benign and malignant spindle cell tumors of soft tissue, skin, serosal surfaces, and gastrointestinal tract

An immunohistochemical study to determine the pattern of immunoreactivity for bcl-2 oncoprotein was performed in 380 spindle cell tumors of soft tissue, skin, serosal surfaces, and gastrointestinal tract. The cases studied included examples of benign, reactive spindle cell proliferations to benign and malignant spindle cell neoplasms, including nodular fasciitis (10), fibromatosis (5), dermatofibroma (10), dermatofibrosarcoma protuberans (18), Kaposi's sarcoma (15), spindle cell lipomatous tumors (24), benign and malignant smooth muscle tumors (35), neural/peripheral nerve sheath neoplasms (53), synovial sarcomas (70) solitary fibrous tumors of serosal surfaces and other sites (56), gastrointestinal stromal tumors (GIST) (47), and malignant undifferentiated fibroblastic spindle cell proliferations of soft tissue (37 cases). The results of bcl-2 staining was additionally correlated with CD34 immunoreactivity. Bcl-2 was uniformly negative in all cases of nodular fasciitis, fibromatosis, and dermatofibroma, as well as in benign and malignant smooth muscle proliferations. Strong positivity for bcl-2 was observed in all cases of spindle cell lipoma, dendritic fibromyxolipoma, Kaposi's sarcoma, solitary fibrous tumors, gastrointestinal stromal tumors, and in the spindle cell component of synovial sarcoma. With the exception of the last, there appeared to be a close correlation between the expression of bcl-2 and CD34 in these tumors. Strong bcl-2 positivity also was found, at least focally, in approximately one third of benign and malignant peripheral nerve sheath tumors, particularly in the better-differentiated (Antoni type A) areas. Sarcomas of fibroblastic type, including low-grade myxofibrosarcoma, malignant fibrous histiocytoma, and fibrosarcoma, showed variable expression of bcl-2 in the tumor cells. Our results appear to indicate that bcl-2 may have a wide distribution among benign and malignant spindle cell neoplasms. Strong expression of this marker in some of these conditions, particularly solitary fibrous tumor, gastrointestinal stromal tumors, and synovial sarcoma, may be of aid for differential diagnosis.

Primary pulmonary ganglioneuroblastoma: a clinicopathologic and immunohistochemical study of two cases

We present two patients with primary ganglioneuroblastoma involving the bronchial wall. The first, a 38-year-old woman, presented with signs and symptoms suggestive of multiple endocrine neoplasia, including gastric ulceration and hypercalcemia. Chest radiographic studies revealed a 3-cm nodule in the hilus of the right lung and two less-pronounced lesions in the periphery of the right lung. The second, a 20-year-old asymptomatic woman, was evaluated for a solitary mass in the upper lobe of the left lung that was peribronchial and that impinged on the lumen of a bronchus. Grossly, both neoplasms extended from bronchi, were well-circumscribed, firm, tan or white, and homogeneous, and measured 5 x 5 cm and 3 x 3 cm, respectively. Histologically, both tumors were characterized by neuroblastoma with areas of neuropil and multifocal areas of ganglion cells. Immunohistochemical studies performed in one case showed focal staining for neurofilament protein and S-100 protein and diffuse staining for neuron-specific enolase. Follow-up information showed that one patient died a few days after admission to the hospital; the second patient has remained well and without evidence of recurrence or metastases 1 year after initial diagnosis. These two cases confirm that ganglioneuroblastoma can occur as a primary pulmonary tumor in adults, presumably arising from sympathetic ganglia of the bronchus.

Dendritic fibromyxolipoma: clinicopathologic study of a distinctive benign soft tissue lesion that may be mistaken for a sarcoma

Twelve cases are described of a distinctive benign soft tissue lesion that may be mistaken for a sarcoma. The tumors occurred in 11 men and a woman aged 33 to 81 years (mean, 64 years), and measured from 2 to 11 cm in greatest diameter (mean, 6 cm). They were grossly described as soft, well-circumscribed, yellow-gray, with a mucoid cut surface. All cases were superficially located in the subcutis or muscular fascia of the head and neck region or the chest and back. Histologically, the tumors were characterized by a proliferation of spindle or stellate fibroblastic cells variably admixed with mature adipose tissue embedded in an abundant myxoid and collagenized stroma. The spindle and stellate fibroblastic cells were characterized by slender dendritic prolongations of their cytoplasm, which appeared to extend for short distances along connective tissue planes. Electron microscopy in two cases confirmed the dendritic nature of the fibroblastic cells, which showed elongated cytoplasmic processes lacking external lamina and displaying foci of pinocytotic activity. Immunohistochemical studies in 11 cases showed strong positivity of the spindle cells with vimentin, CD34 and bcl-2, and negative staining for smooth muscle actin, muscle-specific actin (HHF35), desmin, S-100 protein, keratin, and EMA. Because of their prominent myxoid stroma and relatively large size, some of these tumors were initially misinterpreted as low-grade sarcomas. Clinical follow-up in five cases, however, showed that the patients were alive and well without evidence of recurrence between 5 and 13 years (mean follow-up, 8 years) after simple local excision. The present cases appear to represent a distinctive form of benign soft tissue neoplasm that should be distinguished from myxoid liposarcoma and other benign and malignant myxoid tumors of superficial soft tissues.

Primary pulmonary glomus tumor: a clinicopathologic and immunohistochemical study of two cases

We present two cases of glomus tumors arising within the lung parenchyma. The patients are a 40-year-old man and a 51-year-old man. Clinically, the two men were asymptomatic, and the pulmonary tumor was detected during a routine chest roentgenographic examination. Complete surgical resection of the pulmonary tumors was performed. Grossly, the tumors measured 1.1 and 1.5 cm. in greatest dimension; they were well circumscribed and subpleural. Neither tumor showed evidence of invasion of lung or pleura. Histologically, both tumors had pseudocapsules, lacked invasion of surrounding lung structures, and demonstrated the appearance of the solid/mucohyaline, or "glomus tumor proper" type of neoplasm. This included oval-to-round cells, with central uniform nuclei; variably eosinophilic-to-clear cytoplasm; and well-demarcated cell borders in close proximity to a rich vascular supply showing perivascular fibrosis. Immunohistochemically, both tumors showed diffuse, moderate-to-strong staining for vimentin, muscle-specific actin, and smooth muscle actin. One tumor also showed diffuse strong staining for desmin, whereas the other was negative. Follow-up information obtained from one of the patients revealed that he was alive and well 47 months after surgical resection. Our cases highlight the ubiquitous distribution of glomus tumor and its similar histologic appearance and immunohistochemical profile to soft tissue glomus tumors.

Solitary fibrous tumor of the liver: a clinicopathologic and immunohistochemical study of nine cases

Nine cases of primary solitary fibrous tumors of the liver are presented. The patients are 7 women and 2 men between the ages of 32 and 83 years (mean, 57.5 years). Clinically, palpable masses were detected during physical examination in five patients. Two patients presented with symptoms of cholecystitis, one with hematuria, one with periumbilical pain, and one with hypoglycemia. One patient was found to have an abdominal mass during follow-up evaluation for colonic carcinoma, whereas in one patient the tumor was an incidental finding at autopsy. Two patients were asymptomatic, and the tumor masses were detected during a routine physical examination. Grossly, the tumors varied in size from 2 to more than 20 cm in greatest dimension and were described as firm, white-to-gray, well or ill defined. Eight tumors were described as intraparenchymal lesions, two were grossly necrotic, and one tumor was attached by a pedicle to the liver capsule without infiltration into the liver parenchyma. Histologically, most of the tumors had a bland appearance with the classic short storiform (so-called patternless) pattern and absence of cellular atypia, mitoses and/or necrosis. However, in two cases, there was marked cellular atypia and mitotic figures varying from 2 to 4 mitoses per 10 high power field (hpf). Immunohistochemically, all the tumors showed a strong positive reaction against antibodies for CD-34 and vimentin. Follow-up information showed that two patients died within days of postsurgical resection of the tumor, whereas one was alive and well 1 year after initial diagnosis. No follow-up information was available for the other five patients. The cases herein presented highlight the ubiquitous distribution of this neoplasm and the similar clinical and histopathological features to those observed in serosal surfaces. Solitary fibrous tumors of the liver, although rare, need to be considered in the differential diagnosis of mesenchymal lesions of the liver.

Pulmonary plasmacytomas: a clinicopathologic and immunohistochemical study of five cases

Five cases of primary plasmacytoma of the lung are presented. The patients were four men and one woman between the ages of 50 and 79 years (mean age, 57 years; median age, 54 years). Two patients presented with symptoms related to their tumor; these included cough, dyspnea, and hemoptysis. In two patients, the tumor presented as a hilar mass, whereas in the remaining three patients, the tumor was located intraparenchymally. Clinically, only one patient had a reported monoclonal gammopathy (IgG, kappa). Because of the proximal location of these tumors, three patients underwent pneumonectomy; one other underwent a lobectomy, and one had a segmental resection. Grossly, the tumors ranged from 2.5 to 8 cm in maximum diameter (mean, 4.4 cm); they were either peribronchial or involved a major bronchus. Histologically, they were characterized by sheets of plasma cells that were well differentiated in two cases and moderately differentiated in three. Amyloid was present in two cases. In four tumors, there was a monoclonal population of lambda light chain-bearing plasma cells, whereas in one, the plasma cells expressed a monoclonal kappa light chain. The tumor cells predominantly expressed IgG heavy chains in two cases. Peribronchial and mediastinal lymph nodes were involved in three cases. Follow-up information ranged from 4 days to 262 months (average, 115 months; median, 36 months). Two patients survived more than 20 years before dying of non-tumor-related causes. Two patients died 28 months and 4 days after surgery with concurrent tumor in liver and mediastinal and para-aortic lymph nodes. Comparing the present cases and those reported in the literature, we noted that the patients herein presented are, on average, older than those published previously. Combining our cases with 14 other verifiable, previously published cases, the overall 2- and 5-year survivals of pulmonary plasmacytomas are 66% and 40%, respectively. Patients with pulmonary plasmacytomas can have a long-term survival, as evidenced by two of our patients who survived 20 or more years.

Germ-cell tumors of the mediastinum

Germ-cell tumors occurring primarily in the mediastinum have been well recognized in the literature for many years. Unfortunately, most of what has been written on these tumors has been in the form of case reports and small series of cases, thus precluding a better understanding of their clinical and demographic features, as well as of their biologic behavior in this particular location. In addition, mediastinal germ-cell tumors not only have never had a standardized nomenclature, but they also have lacked the benefit of a clinical staging scheme for assessment of prognosis. Another important aspect of these tumors that has required attention is the frequency with which teratomatous lesions are associated with malignant components in the mediastinum. Comprehensive studies of mediastinal germ-cell tumors to determine whether these lesions recapitulate the distribution, histopathologic features, and biologic behavior of their counterparts in other areas, such as the gonads, have been lacking for many years. In this article, we review our experience with a large series of cases of primary mediastinal germ cell tumors and examine recent concepts and advances in our understanding of these unusual and diagnostically challenging neoplasms.

Primary alveolar soft-part sarcoma of the mediastinum: a clinicopathological and immunohistochemical study of two cases

AIMS

Primary alveolar soft part sarcomas originating within the thoracic cavity are rare. The cases herein described highlight the ubiquitous distribution of this neoplasm and the importance of considering this tumour in the differential diagnosis of mediastinal tumours.

METHODS AND RESULTS

Two cases of alveolar soft-part sarcoma of the mediastinum are presented. The patients are two men of 22 and 23 years of age. Clinically, the patients presented with symptoms of chest pain. One tumour was in the anterior mediastinum while the second tumour was in the posterior mediastinum. Even though the bulk of the tumours were in mediastinal locations, both patients had pulmonary metastases at the time of diagnosis. Histologically, both tumours showed the classic morphology of alveolar soft part sarcoma, i.e. a proliferation of large polygonal cells with round to oval nuclei, prominent nucleoli and moderate amounts of eosinophilic cytoplasm arranged in a prominent alveolar pattern. Periodic acid-Schiff stains showed the characteristic diastase-resistant intracytoplasmic crystals. Immunohistochemical studies showed focal myoglobin reactivity in one case, while cytokeratin, vimentin, S100 protein, chromogranin, synaptophysin, neurofilaments, leu-enkephalin, desmin, smooth muscle actin and muscle-specific actin were negative in both cases. The patient with the anterior mediastinal tumour died of disease 14 months after diagnosis, and the patient with the posterior mediastinal mass remained well for at least 15 years and was later lost to follow-up.

CONCLUSIONS

As has been observed in other anatomic areas, namely soft tissues, alveolar soft part sarcomas may follow an uncertain natural history. Interestingly, in our cases, the tumour in the anterior mediastinum followed a fatal course raising the possibility that the anatomic location of the tumour may have play a role in the behaviour of the tumour.

Thymoma with pseudosarcomatous stroma: report of an unusual histologic variant of thymic epithelial neoplasm that may simulate carcinosarcoma

Six cases are described of an unusual type of primary thymic epithelial neoplasm characterized by a biphasic epithelial/spindle cell morphology that closely resembled a carcinosarcoma. The patients were two women and four men 28-70 years of age. The tumors presented clinically as asymptomatic anterior mediastinal masses found incidentally on routine chest radiographs. All patients were treated by complete surgical excision. Grossly, the tumors consisted of well-circumscribed, encapsulated masses that measured 6-14 cm in greatest diameter and showed a gray-white, homogeneous, rubbery cut surface. Histologically, the lesions were composed of anastomosing islands and cords of oval to polygonal epithelial cells displaying large nuclei with occasional prominent nucleoli and rare mitotic figures, separated by areas containing a highly cellular spindle cell proliferation without nuclear atypia. Thymic remnants could be identified in the periphery of the lesions in four cases. Immunohistochemical stains showed diffuse strong positivity for keratin and focally for epithelial membrane antigen (EMA) in the epithelial cell component, and strong positivity for vimentin and focally for actin in the spindle cell stromal component. Stains for keratin, EMA, desmin, S-100 protein, and CD34 were negative in the spindle stromal cells in all cases except one, in which EMA positivity was present; CD5 stains were negative in the epithelial cells in all cases examined. Electron microscopic examination in one case showed well-formed desmosomes and tonofilaments in the epithelial elements, as well as features indicative of fibroblastic differentiation in the spindle stromal cells. Because of the unusually florid spindle cell stromal component and the focally atypical features of the epithelial cells, some of these tumors initially were misinterpreted as examples of carcinosarcoma. Clinical follow-up in five cases showed that the patients were alive and without evidence of disease over a period of 5-20 years (mean follow-up 10 years), suggesting a benign or very low grade malignant biologic behavior. The present cases appear to represent an unusual, previously undescribed morphologic variant of thymoma characterized by a prominent pseudosarcomatous stromal component. Because of the distinctive histologic appearance and indolent clinical behavior, these lesions should be distinguished from other more aggressive anterior mediastinal neoplasms displaying a biphasic morphology.

Hepatoid yolk sac tumors of the mediastinum: a clinicopathologic and immunohistochemical study of four cases

Four cases of primary hepatoid yolk sac tumors of the anterior mediastinum are described. The patients were all men between the ages of 26 and 40 years (median 33). Clinically, they all presented with a history of shortness of breath and chest pain of several weeks' duration. None of the patients had a history of germ cell tumor elsewhere or evidence of any hepatic abnormality. Grossly, all the tumors were described as large mediastinal masses that impinged on adjacent structures. Histologically, they were characterized by sheets of medium-sized, round to polygonal neoplastic cells with moderate amounts of eosinophilic cytoplasm and round to oval nuclei with prominent nucleoli. The cellular proliferation was homogeneous and displayed moderate cellular atypia and scattered mitotic activity. All the tumors showed focally the presence of more conventional areas of yolk sac tumor, with islands of tumor cells showing a reticular pattern of growth admixed with scattered intra- and extracellular hyaline globules and occasional Schiller-Duval bodies. Immunohistochemical studies showed strong positivity of the tumor cells for alpha-fetoprotein in both components of the lesions. Follow-up information was available in three patients, all of whom developed lung metastases within a year after initial diagnosis. Two of these patients died of tumor within the same period, whereas a third patient has been lost to follow-up. The present cases illustrate an unusual histologic pattern of yolk sac tumor in the mediastinum and highlight the importance of considering this tumor in the differential diagnosis of lesions showing a hepatoid pattern of growth in the mediastinal area.

Primary melanoma of the lung: a clinicopathologic and immunohistochemical study of eight cases

Primary malignant melanoma of the lung (PMML) is an uncommon neoplasm that may be confused with more conventional types of lung cancer. Although the previously proposed criteria for diagnosis, including the presence of an in situ component, are often difficult to satisfy, this lesion is characterized by a poor prognosis, ultimately leading to patient death. We report eight cases of PMML that presented as solitary, central endobronchial neoplasms, resulting in a picture that closely resembled carcinoid tumor or poorly differentiated non-small-cell carcinoma of the lung. The mean age at diagnosis was 51 years (range 45-71). The patients included one woman and seven men. The histologic growth pattern varied from organoid to fascicular and included epithelioid to spindled cells with hyperchromatic to vesicular nuclei, prominent eosinophilic nucleoli, and abundant eosinophilic to clear cytoplasm with occasional intranuclear cytoplasmic inclusions. A bronchial in situ component was present in four cases. Initial interpretations included carcinoid tumor, non-small-cell carcinoma, and malignant melanoma. Melanin was present in all neoplasms on hematoxylin and eosin staining, although very focally in one case, and was Fontana-Masson positive in all cases. Immunohistochemically, diffuse strong positivity for S-100, HMB-45, and vimentin was present in all seven tumors tested. All seven tumors were negative for cytokeratin, CAM 5.2, and chromogranin. Ultrastructural examination of the eighth case showed dysmorphic premelanosomes but no neurosecretory granules. None of the patients had disseminated disease at presentation, and all patients underwent surgical resection (seven lobectomies and one excision). In this series, primary malignant melanoma of the lung was characterized by an aggressive postoperative course, with five patients dying of metastatic disease from 4 to 32 months after resection (median 14 months). Two patients are alive with metastatic disease at 4 and 30 months after surgery, and the eighth patient is alive with no evidence of disease 108 months after surgery at last follow-up. Metastatic melanoma was identified in various sites, including the lungs, adrenal glands, liver, mesentery, brain, and bone. The cases herein presented indicate that PMML should be included in the differential diagnosis of primary bronchial tumors.

Yolk sac tumors of the mediastinum with prominent spindle cell features: a clinicopathologic study of three cases

Three cases of primary mediastinal yolk sac tumors with prominent spindle cell features are presented. The patients were three men 24-34 years of age (mean 29). Clinically, two patients presented with symptoms of chest pain and cough; no clinical information was provided for the third patient. Grossly, the tumors were described as large mediastinal masses, with a hemorrhagic and necrotic cut surface. Histologically, the tumors were characterized by a predominantly atypical spindle cell proliferation admixed with areas that showed focally the characteristic reticular growth pattern of yolk sac tumors, with the presence of Schiller-Duval bodies and intra- and extracellular hyaline globules. Immunohistochemical studies performed in one case showed positive staining for keratin and alpha-fetoprotein in both the spindle cell and reticular components of the tumor. Follow-up information was obtained in two patients; they both died of tumor with metastases to the lungs 1 year after initial diagnosis. The present cases expand the spectrum of histopathologic growth patterns that may be observed in yolk sac tumors of the mediastinum and stress the issue of careful sampling and evaluation of mediastinal neoplasms for arriving at the correct diagnosis.

Primary mediastinal choriocarcinomas: a clinicopathologic and immunohistochemical study of eight cases

Primary choriocarcinoma of the anterior mediastinum is by far the rarest and most controversial form of extragonadal germ cell tumor. A clinicopathologic study of eight primary mediastinal neoplasms bearing the histopathologic and immunohistochemical features of choriocarcinoma is presented. The patients were all men between the ages of 21 and 63 years (mean, 42 years). Clinical symptoms included shortness of breath, chest pain, cough, and superior vena cava syndrome; one patient also had gynecomastia. All patients presented with large anterior mediastinal masses on chest radiographs that measured an average of 10 cm in greatest diameter. Grossly, the tumors were described as large, soft, extensively hemorrhagic, and with foci of necrosis. Histologically, they were characterized by a dual cell population composed of cytotrophoblastic cells with uniform, round nuclei, clear cytoplasm, and prominent nucleoli admixed with large, multinucleated syncytiotrophoblastic cells with bizarre nuclei, prominent nucleoli, and abundant eosinophilic cytoplasm. Immunohistochemically, the tumors were notable for strong keratin and beta-human chorionic gonadotropin (HCG) positivity. Seven patients presented at the time of diagnosis with thoracic and extrathoracic (liver, adrenal, kidney, and spleen) metastases. In one case, the tumor was entirely confined to the mediastinum. All patients died over a period of 1 to 2 months. Complete autopsies were performed in all cases; none of the patients showed evidence of a testicular tumor or scar after thorough examination of the testes on serial sectioning. The present cases demonstrate the widespread distribution of germ cells in the human body and lend further support to the existence of primary extragonadal choriocarcinoma arising in the thymic region.

Primary germ cell tumors of the mediastinum: I. Analysis of 322 cases with special emphasis on teratomatous lesions and a proposal for histopathologic classification and clinical staging

BACKGROUND

Primary germ cell tumors of the mediastinum are unusual neoplasms with histopathologic features that are similar to those of germ cell tumors in the gonads. However, their clinical features, behavior, and spectrum of pathologic features in the mediastinum have not yet been fully defined.

METHODS

The clinical and pathologic features of 322 cases of primary mediastinal germ cell tumors were reviewed, with special emphasis on teratomatous lesions. The tumors were divided into groups according to their histologic features and correlated with their order of frequency, patient gender and age distribution, and morphologic features. A clinical staging scheme based on the extent and location of the lesions was devised.

RESULTS

The overwhelming majority of patients were men (320); only 2 were women (both had teratomatous lesions with additional malignant components). The patients' ages ranged from 1 to 79 years (mean, 40 years). Histologically, all types of germ cell tumors were represented, including 138 teratomas (87 mature teratomas, 6 immature teratomas, and 45 teratomas with additional malignant components); 120 seminomas; 52 nonseminomatous, nonteratomatous germ cell tumors (38 yolk sac tumors, 6 embryonal carcinomas, and 8 choriocarcinomas); and 12 combined germ cell tumors without teratomatous components. The teratomatous lesions with additional malignant components were further separated into subtypes based on the histologic types of their malignant components, i.e., epithelial, mesenchymal, etc. Clinical staging was possible in 242 cases, with 191 cases (79%) in Stage I, 4 cases (1.6%) in Stage II, and 47 cases (19.4%) in Stage III. In each group, the clinical staging correlated well with the clinical outcome for the majority of patients.

CONCLUSIONS

The results of this study showed that mediastinal germ cell tumors have demographic and histopathologic distributions similar to those of tumors occurring in the male gonads, with teratomatous and seminomatous lesions being the most common. Among the nonseminomatous germ cell tumors in this study, the yolk sac tumors appeared to occur the most frequently (the ratio of yolk sac tumor occurrence to embryonal carcinoma occurrence was 6.1:1). In addition, the subclassification of teratomas with additional malignant components based on the histologic types of malignancies may lead to more therapy choices for patients. At the same time, the use of a clinical staging scheme may be of value in predicting clinical outcome and planning therapy.

Primary germ cell tumors of the mediastinum: III. Yolk sac tumor, embryonal carcinoma, choriocarcinoma, and combined nonteratomatous germ cell tumors of the mediastinum--a clinicopathologic and immunohistochemical study of 64 cases

BACKGROUND

Yolk sac tumor (YST), embryonal carcinoma (EC), choriocarcinoma (CC), and combined germ cell tumors (CGCTs) of the mediastinum are uncommon neoplasms. Only sporadic cases have been documented in the literature; therefore, the clinical behavior of these tumors when located in the mediastinum remains relatively unknown.

METHODS

The clinical and pathologic features of 64 cases of primary YST, EC, CC, and CGCTs without teratomatous components were reviewed. The immunohistochemical findings in 29 cases were also analyzed using a panel of monoclonal and polyclonal antibodies in formalin fixed, paraffin embedded tissues.

RESULTS

The patients were all men between the ages of 14 and 63 years (mean, 38.5 years). Their clinical symptoms included chest pain, shortness of breath, chills, fever, and superior vena cava syndrome. None of the patients had a previous history of testicular neoplasm or tumor elsewhere. Macroscopically, the lesions in 27 patients were described as large, soft, hemorrhagic, and in some cases necrotic, and varied in greatest dimension from 6 to 20 cm. Histologically, the tumors displayed morphologic features similar to those of their gonadal counterparts. Pure YSTs accounted for the majority of cases in this series (38 of 64, 60%), followed by pure CCs (8 of 64, 12%) and pure ECs (6 of 64, 9%). CGCTs accounted for only 18% of the total cases (12 of 64). YSTs showed a variety of growth patterns; however, the reticular pattern was the most commonly observed. ECs showed a more solid growth pattern with marked pleomorphism of the tumor cells and abundant areas of necrosis. CCs were characterized by the presence of cytotrophoblastic and syncytiotrophoblastic elements with frequent areas of necrosis and hemorrhage. The cases of nonteratomatous CGCT consisted of 5 cases of EC + YST, 2 cases of EC + seminoma, 4 cases of YST + seminoma, and 1 case of EC + CC. In clinical staging, 14 patients were Stage I, 6 were Stage II, and 19 were Stage III. Information on follow-up ranging from 1 month to 13 years was available for 40 patients. Seventeen patients with YST died of their tumors. Of these, 10 who presented with Stage III disease died within the first 2 years. Unfortunately, no clinical staging was obtained for the other 7 patients in this group, and they died within 6-36 months. It is noteworthy that 4 patients with YST have survived for more than 2 years; these patients presented in Stages I and II, and 2 of them received aggressive therapy with chemotherapeutic agents and radiation. Two patients with Stage III EC died within 2 years. The remaining 4 patients with EC were lost to follow-up. Eight patients with CC died within 6 months after initial diagnosis; 7 of them presented Stage III disease and only 1 presented with Stage I. In the nonteratomatous CGCT category, 2 patients with EC + YST died within 2 years after initial diagnosis, whereas 3 patients with YST + seminoma were alive after 4-9 years.

CONCLUSIONS

The results of this study confirm the aggressive nature of primary nonseminomatous germ cell tumor of the mediastinum; 72% of the patients with adequate follow-up died of their tumors within 6-36 months after diagnosis, despite aggressive therapy. Clinical and pathologic staging of mediastinal YST, EC, and CGCT are important parameters that may be helpful in predicting the clinical outcomes of patients with these tumors. The authors' findings suggest that the majority of tumors that are not limited to the mediastinum at the time of diagnosis have more aggressive behavior. On the other hand, mediastinal choriocarcinomas appeared to follow a very aggressive clinical course, regardless of treatment modality or clinical tumor stage.

Primary germ cell tumors of the mediastinum: II. Mediastinal seminomas--a clinicopathologic and immunohistochemical study of 120 cases

BACKGROUND

Primary seminomas of the mediastinum are unusual neoplasms that are morphologically indistinguishable from their gonadal counterparts but may have different biologic behavior because they arise at this particular location.

METHODS

The clinical and pathologic features in 120 cases of primary mediastinal seminoma were reviewed, and the immunohistochemical staining patterns in 50 of these tumors were also analyzed.

RESULTS

The patients were all men between the ages of 14 and 79 years (mean age, 46.5 years). Their clinical symptoms included cough, chest pain, and dyspnea. In some patients, the lesions were asymptomatic and discovered incidentally on routine chest radiographs. None of the patients had a previous history of testicular neoplasm or tumor elsewhere. Macroscopically, the tumors were described as soft and tan, with a slightly lobulated cut surface, and measured up to 16 cm in greatest dimension. Histologically, the morphologic features were similar to those of tumors occurring in the gonads, namely, a neoplastic proliferation of round-to-polygonal cells with indistinct cell borders, clear-to-lightly-eosinophilic cytoplasm with round-to-oval nuclei and prominent nucleoli, associated with a prominent inflammatory background composed mainly of mature lymphocytes. Necrosis, hemorrhage, multinucleated giant cells, granulomatous reaction, and remnants of thymic tissue were observed in a variable number of cases; mitoses were rare. Immunohistochemical studies in 50 cases showed cytoplasmic staining with placental alkaline phosphatase in 80% of the tumors, focal dotlike positivity for CAM 5.2 low-molecular-weight keratins in 75%, focal cytoplasmic staining for wide-spectrum keratin in 70%, focal positive reaction with vimentin in 70%, and focal positivity with HCG in singly scattered cells in 5%. Immunostains for carcinoembryonic antigen, epithelial membrane antigen, and alpha-fetoprotein were negative in all the cases studied. Fifty patients were Stage I, 3 patients were Stage II, and 12 patients were Stage III. Clinical follow-up information was obtained for 65 cases (54%). Forty-nine patients were alive and disease free after a period ranging from 1 to 19 years (mean follow-up, 10 years). Sixteen patients died within the same period and were found to have metastases to distant organs. Of the 16 patients who died, 6 showed extension of the tumor outside of the mediastinal compartment at the time of initial diagnosis (Stage III lesions). Aside from clinical staging, the authors' findings also suggest that patients >37 years have worse outcomes than younger individuals. The authors were unable to find any correlation between histopathologic features and clinical behavior in any of these cases.

CONCLUSIONS

Clinical and pathologic staging of mediastinal seminomas are important parameters that can be useful in determining the clinical outcomes of patients with these tumors. Tumor invasion into adjacent organs represents a marker of increased morbidity and mortality. The authors' findings suggest that patients with mediastinal seminomas may have a very good prognosis when the diagnosis is made early; patients with more advanced lesions may require more aggressive therapy for improved local control and prevention of distant metastases.

Primary spinal paragangliomas: a clinicopathological and immunohistochemical study of 30 cases

AIMS

Extra-adrenal paragliomas are neoplasms which have been the subject of much debate regarding parameters to establish their biological behaviour. This study describes the clinicopathological and immunohistochemical features of 30 cases of spinal paragliomas.

METHODS AND RESULTS

There were 15 male and 15 female patients. The median age at diagnosis was 46 years (range 20-74 years). Fourteen patients presented with back pain, two with numbness of the lower extremities, one with difficulty in walking and one with spinal cord compression. Nineteen tumours were located in the lumbar region, six in the cauda equina, two in the filum terminale, two in the thoracic region and one in the cervical region. All patients underwent gross total excision. The size of the tumours ranged from 10 to 50 mm. Histologically, 18 neoplasms showed alveolar (Zellballen) pattern, seven a spindle component, two eosinophilic granular cells suggestive of oncocytic metaplasia, two melanin pigment and one ganglion cells. Positive immunohistochemical results include: neuron-specific enolase 23/23 (100%), synaptophysin 21/23 (91%), S100 protein 22/23 (95%, sustentacular cells), leu-enkephalin 11/23 (47%), somatostatin 8/23 (34%), focal glial fibrillary acidic protein 7/23 (30%), focal keratin 5/23 (21%), neurofilament proteins 3/23 (13%) and adrenocorticotrophic hormine (ACTH) 1/23 (4%). Follow-up information obtained in 20 patients show 17 patients alive over a period of 6-216 months. One patient had bone metastases. Two patients died of unrelated causes, including one of congestive heart failure and one of myocardial infarction.

CONCLUSIONS

In our experience, spinal paragangliomas behave as slow-growing tumours susceptible to potential cure by total excision. We agree with the current World Health Organization (WHO) classification as grade I tumours. Less than 1% may be locally aggressive. Spinal paragangliomas immunoreact not only for conventional neuroendocrine markers but also for peptides including somatostatin and ACTH and focally for the epithelial marker keratin.

Pulmonary lipomatosis: a variant of placental transmogrification

An unusual pulmonary lesion is presented. The patient is a 55-year-old white man with a 2-week history of pleuritic chest pain, shortness of breath, and bronchopneumonia. The patient had also a history of smoking and chronic cough for 12 years. Chest radiographic studies showed a 20-cm bulla in the left upper lobe. A left upper lobectomy was performed obtaining an almost completely collapsed lobe with destruction of the normal architecture by a meshwork of yellowish tissue. Histologically, there were strikingly papillary structures composed almost exclusively of mature adipose tissue with small collections of inflammatory cells. Minimal emphysema in the adjacent lung parenchyma was observed. The case herein presented most likely represents part of the spectrum of placental transmogrification or placentoid bullous lesions of the lung.

Mediastinal yolk sac tumors associated with prominent multilocular cystic changes of thymic epithelium: a clinicopathologic and immunohistochemical study of five cases

Five cases of yolk sac tumor of the anterior mediastinum associated with prominent thymic cystic changes are presented. The patients were five men between the ages of 17 and 22 years (mean, 19.5 yr). Clinically, four patients presented with symptoms of chest pain and shortness of breath, whereas the fifth was asymptomatic: his tumor was discovered during a routine physical examination. None of the patients had a history of previous tumor elsewhere. Grossly, the tumors were described as cystic lesions measuring between 8 and 12 cm in greatest dimension. Histologically, the tumors showed prominent cystic changes reminiscent of those observed in acquired multilocular thymic cysts, i.e., the presence of cystic cavities lined by squamous epithelium with prominent inflammatory changes, lymphoid hyperplasia, cholesterol cleft granulomas, and remnants of thymic tissue in the walls of the cysts. In addition, there was a neoplastic cellular proliferation composed of small cells with scant cytoplasm, round nuclei, and inconspicuous nucleoli adopting a reticular pattern of growth and, in some areas, embedded in abundant myxoid stroma. Numerous intra- and extracellular hyaline globules, as well as Schiller-Duval bodies, could also be identified. Immunohistochemical studies showed positive reaction with alpha-fetoprotein antibodies in the tumor cells. Follow-up information obtained in these patients showed that all had died of tumor 1 to 3 years after initial diagnosis. The present cases document another unusual but distinctive growth pattern of yolk sac tumor in the mediastinum and highlight the importance of proper sampling of cystic lesions in this location.

Pulmonary alveolar microlithiasis. A clinicopathologic and chemical analysis of seven cases

OBJECTIVE

To determine the clinical features and outcome of patients with pulmonary alveolar microlithiasis and to determine the chemical composition of the microliths.

CASE MATERIAL

We studied seven cases of pulmonary alveolar microlithiasis. The patients were six women and one man, aged 19 to 70 years (mean age 44.5 years). Clinically, five patients were known to have suffered from this condition for 5 to 41 years. One patient presented with shortness of breath, and another had a gradual decrease in exercise tolerance. None of the patients had a previous history of disturbances in metabolism or any other relevant medical condition. Reports on radiographic studies were available in six cases, and chest radiographs were available for review in the seventh case. They all showed diffuse bilateral pulmonary infiltrates. Open lung biopsies were performed in two patients, and autopsy lung material was reviewed in five patients.

RESULTS

Histologically, the lung showed the typical features of pulmonary alveolar microlithiasis, that is, presence of numerous microliths filling the alveolar spaces with either a normal or thickened fibrotic interstitium. Chemical analysis performed on the lung tissue of six of these patients revealed that the microliths consisted principally of calcium and phosphorus salts. Five of these patients died of respiratory failure; however, their deaths occurred from 5 to 41 years following the initial diagnosis. No follow-up information was obtained in two patients.

CONCLUSIONS

The findings of this study confirm that pulmonary alveolar microlithiasis can be seen in any age group and that the microliths are composed principally of salts of calcium and phosphorus. Additionally, these cases confirm that the disease typically follows a protracted course.

Malignant cartilaginous tumors of the mediastinum: clinicopathological study of six cases presenting as extraskeletal soft tissue masses

Cartilage and bone-forming tumors of the mediastinum are extremely rare neoplasms with very few cases having been reported in the literature. We studied six cases of primary malignant cartilaginous tumors presenting as extraskeletal soft tissue masses in the posterior mediastinum. The patients were five women and one man aged 11 to 63 years (median, 31 years). Histologically, the lesions showed a spectrum of features that ranged from mesenchymal chondrosarcoma, to extraskeletal myxoid chondrosarcoma, to moderately well to poorly differentiated chondrosarcoma. In all cases, the lesions presented as well-circumscribed tumor masses centered in the soft tissues in the posterior mediastinum without radiographic evidence of origin from bone. Because of their relatively small size, good circumscription, focal areas of calcification, and posterior mediastinal location, the preoperative clinical diagnoses included benign neurogenic tumor and neuroblastoma. All of the lesions were treated by complete surgical excision, followed in two cases by postoperative radiation therapy. Clinical follow-up was available in five cases: two patients with mesenchymal chondrosarcoma presented with local recurrence after 3 and 7 years, one developed metastases to the sacrum 8 years after initial diagnosis and died, and one was alive and well without evidence of disease after 6 years. The patient with myxoid chondrosarcoma of the posterior mediastinum developed bilateral pulmonary metastases 10 months after surgery and has been lost to follow-up since. Our findings reinforce previous observations on the occurrence of extraskeletal cartilaginous tumors in the mediastinum and indicate that these tumors can show a propensity for local aggressive behavior with high recurrence rate and a definite potential for distant metastases. Such tumors should be considered in the differential diagnosis of malignant neoplasms presenting as a soft tissue mass in the posterior mediastinum.

Epithelial-myoepithelial carcinoma of the lung: immunohistochemical and ultrastructural observations and review of the literature

Epithelial-myoepithelial carcinoma is a rare low-grade malignant salivary gland neoplasm that most commonly occurs in the parotid gland but can also arise in minor salivary glands. We report a case of a primary epithelial-myoepithelial carcinoma of the lung. The patient is a 55-year-old black woman who presented with increasing shortness of breath and productive cough of at least 3 months duration. A left lower lobe endobronchial lesion was identified radiographically. Surgical resection of the lesion was performed, obtaining a circumscribed, nonencapsulated 3.9 cm tan mass which was attached to the inner wall of the lateral basal segment bronchus. A biphasic proliferation of epithelial (cytokeratin positive; S-100 protein and muscle-specific actin negative) and myoepithelial (S-100 protein and muscle-specific actin positive with focal weak cytokeratin positive) cells was identified by immunohistochemical and ultrastructural analysis of formalin-fixed tissue. The patient is disease free 7 months after resection. Pulmonary epithelial-myoepithelial carcinoma likely derives from the submucosal bronchial glands and should be added to the growing list of salivary gland-type neoplasms that may occur as primary pulmonary neoplasms. Because its histology is identical to salivary epithelial-myoepithelial carcinoma, pulmonary epithelial-myoepithelial carcinoma should be considered a low-grade malignant neoplasm and should be designated as epithelial-myoepithelial carcinoma is preference to other terms that may not convey its malignant potential. Although follow-up on reported cases is limited, lobectomy with negative bronchial margin should be curative.

Inflammatory pseudotumor of lymph nodes: a study of 25 cases with emphasis on morphological heterogeneity

The clinicopathological and immunohistochemical findings in 25 cases of inflammatory pseudotumor of lymph nodes (IPT) are presented. The patients were 13 women and 12 men between 8 and 81 years of age. Clinically, symptoms of prior infection, fatigue, abdominal pain, weight loss, fever of unknown origin, pelvic inflammatory disease, or nausea and night sweats were obtained in 15 patients, whereas six patients presented with asymptomatic lymphadenopathy. In four additional patients, no clinical information was obtained. The involved nodes included cervical, supraclavicular, inguinal, mesenteric, and mediastinal lymph nodes. In two cases, there was synchronous involvement of separate lymph node groups (inguinal and cervical in one case and cervical and mediastinal in another case), whereas in a third patient there was synchronous involvement of the spleen and a paraaortic lymph node. Histologically, the lesions were characterized by a fibrosing/inflammatory process that showed marked heterogeneity and striking variation from case to case. Based on their histological features, the lesions could be classified into three different groups: Stage I was characterized by the appearance of single or multiple small foci containing a spindle cell proliferation admixed with a prominent inflammatory background, with complete preservation of the remainder of the nodal architecture; stage II was characterized by more diffuse involvement of the lymph node with a marked inflammatory response admixed with a prominent myofibroblastic proliferation leading to subtotal effacement of the nodal architecture, often with extension of the process beyond the capsule into perinodal fat; and stage III was characterized by almost complete replacement of the lymph node by diffuse sclerosis with scant residual inflammatory elements and total loss of the normal nodal architecture. Immunohistochemical studies in 20 cases showed a striking number of vimentin- and actin-positive myofibroblastic cells with moderate increase in CD20/CD45+ small lymphocytes and polyclonal plasma cells in the stage I lesions, the emergence of numerous CD68+ histiocytes admixed with lymphocytes, plasma cells, and abundant fibromyofibroblastic cells in the stage II lesions, and only few remaining scattered CD68+ histiocytes and fibroblasts in the stage III lesions. Our findings suggest that inflammatory pseudotumor of lymph node represents an evolving, dynamic process that may adopt different morphological appearances depending on its stage of evolution. Recognition of the various stages of this process may be of importance for differential diagnosis with other fibrosing/inflammatory conditions of lymph nodes.

Primary malignant 'triton' tumour of the lung

Two cases of malignant 'triton' tumour arising within lung parenchyma are described. The patients were a three-year-old child and a 53-year-old man. Both patients presented with shortness of breath and a large intrapulmonary mass on chest X-ray. Neither patient had a history of von Recklinhausen's neurofibromatosis. The lesions were treated by pneumonectomy. Grossly, both tumours presented as large, soft and gelatinous intraparenchymatous masses measuring 130 mm and 80 mm, respectively. Histologically, they were characterized by an atypical spindle cell proliferation embedded in an abundant myxoid stroma. Focal areas of rhabdomyoblastic differentiation characterized by large cells with abundant eosinophilic cytoplasm and occasional cytoplasmic cross-striations could be seen admixed with the atypical spindle cell elements. Immunohistochemical studies showed a focal positive reaction for S-100 protein in the atypical spindle cells embedded within the myxoid stroma, and a strong positive reaction for desmin and myoglobin in the rhabdomyoblastic areas. The child died three months after diagnosis with extension of the tumour into the thoracic cavity. The second patient has been lost to follow-up. Although rare, malignant 'triton' tumour should be considered in the differential diagnosis of primary spindle cell sarcomas of the lung.

Primary leiomyosarcomas of the lung: a clinicopathologic and immunohistochemical study of 18 cases

We studied 18 patients with primary malignant smooth muscle tumors of the lung (7 women and 11 men, 5-76 yr old, with a mean age of 50 yr). Lesions varied from 1.7 to 10 cm in greatest diameter. The tumors were classified as low (4 cases), intermediate (2), or high grade (12). Low-grade lesions were characterized by an orderly proliferation of fascicles of spindle cells that intersected at right angles and showed oval-to-spindle cells with cigar-shaped nuclei, minimal pleomorphism, and low mitotic activity, without hemorrhage or necrosis. Intermediate-grade lesions retained the fascicular configuration but showed increased cellularity with atypia and dense chromatin pattern, occasional pleomorphism, and mild increase in mitotic activity. High-grade lesions showed high cellularity, marked pleomorphism and atypia, frequent areas of hemorrhage and necrosis, and high mitotic activity. Immunohistochemical studies in 16 cases showed positive staining of tumor cells with smooth muscle actin in 12, desmin in 5, and coexpression of actin and/or desmin and keratin in 3. Six patients with low- and intermediate-grade lesions were alive and well from 2 to 12 years after diagnosis (mean follow-up time, 6 yr); 8 with high-grade lesions died of their tumors with widespread metastases from 1 to 24 months after diagnosis (median survival time, 5 mo). One patient whose tumor showed features of high-grade leiomyosarcoma was alive and well 12 years after surgery. Three patients with high-grade tumors were lost to follow-up. Our findings suggest that histologic grade may be the most reliable prognostic parameter for predicting clinical behavior in primary leiomyosarcoma of the lung and that smooth muscle actin is the most sensitive immunohistochemical marker for establishing the diagnosis in these tumors. Primary leiomyosarcoma should be considered in the differential diagnosis of pulmonary spindle cell neoplasms; histologic grading may be of value in the planning of therapy and assessment of prognosis for these lesions.

Pigmented extraadrenal paragangliomas. A clinicopathologic and immunohistochemical study of five cases

BACKGROUND

Pigmented extraadrenal paragangliomas are unusual neoplasms that have rarely been reported in the literature.

METHODS

The clinical, pathologic, and immunohistochemical features of five cases of pigmented extraadrenal paragangliomas were reviewed.

RESULTS

The patients were 2 women and 3 men within the ages of 17 and 56 years (mean age: 36.5). Two neoplasms were located in the lumbar spine, one in the urinary bladder, one in the anterior mediastinum, and one in the retroperitoneum. Clinically, one patient with spinal paraganglioma presented with symptoms of numbness and weakness of the lower extremities whereas the second patient had low back pain of several weeks' duration. The paraganglioma of the bladder occurred in a pregnant woman who had symptoms of dysuria and microscopic hematuria whereas the patient with an anterior mediastinal tumor presented with chest pain. No clinical history was obtained from the patient with the retroperitoneal tumor. None of the patients had a history of hypertension. Grossly, the tumors were described as well-circumscribed, soft, and slightly hemorrhagic, and measured from 2 to 9 cm in greatest dimension. Histologically, the five tumors displayed characteristics similar to those described in these tumors, mainly the presence of an organoid or zellballen growth pattern. In addition, they contained moderate amounts of intracellular melanin pigment that focally obscured the true nature of the lesion. Immunohistochemically, four cases were positive for chromogranin whereas S-100 protein was detected in the sustentacular cells in four cases. Follow-up information ranging from 6 months to 18 years for 3 patients revealed that the patients were alive and well without recurrence or metastasis. One patient with spinal paraganglioma was lost to follow-up, and the patient with mediastinal paraganglioma was a recent case and therefore the behavior of the paraganglioma could not be assessed.

CONCLUSIONS

The current study expands the morphologic spectrum of extraadrenal paragangliomas and emphasizes the need to consider these tumors in the differential diagnosis of pigmented neoplasms. These findings suggest that the presence of melanin pigment does not alter the behavior of these neoplasms.

Primary thymic epithelial neoplasms showing combined features of thymoma and thymic carcinoma. A clinicopathologic study of 22 cases

Thymic epithelial neoplasms are unusual tumors that may span the gamut from clinically benign, well-differentiated lesions (encapsulated thymoma) to overtly malignant, poorly differentiated neoplasms (thymic carcinoma). It has been commonly believed that lesions displaying obvious cytologic features of malignancy (i.e., thymic carcinoma) represent a unique and separate group that is histogenetically distinct from thymoma. We have studied 22 cases of thymic epithelial neoplasms characterized by the admixture of areas displaying conventional features of thymoma with areas showing features of thymic carcinoma. The tumors occurred in six women and 16 men whose ages ranged from 23 to 83 years (median, 53). The lesions presented in eight patients with symptoms of chest discomfort resulting from the involvement of surrounding structures; in 14 patients, they were asymptomatic and discovered incidentally on routine chest radiographs. Histologically, most tumors showed a combination of conventional thymomatous elements with well-differentiated squamous-cell carcinoma (10 cases), followed by thymoma and poorly-differentiated squamous carcinoma (seven cases) and spindle-cell thymoma with poorly-differentiated squamous carcinoma (five cases). Areas of transition between the two different components could be identified in most cases. In five cases, areas showing the features of clear-cell carcinoma could be seen either arising from squamous carcinomatous elements or within the thymomatous component, and in one case transitions between lymphoepithelioma-like carcinoma and anaplastic carcinoma could be observed. Two patients had a history of myasthenia gravis with biopsy-proven thymomas in whom the tumors had been monitored without treatment for 10 and 14 years before the sudden enlargement of the mass. The resected specimens in both patients showed the emergence of a carcinoma arising from a thymoma. The present cases appear to support the existence of a continuum in the spectrum of differentiation between thymoma and thymic carcinoma, suggesting a close histogenetic relationship between these two conditions. Such findings are important not only for our understanding of these tumors but may also play a significant role in the assessment of the biologic behavior and management of these lesions.

Primary intrapulmonary meningiomas. A clinicopathologic and immunohistochemical study of ten cases

BACKGROUND

Primary intrapulmonary meningiomas are rare, and their occurrence has been reported in the literature only sporadically.

METHODS

The clinical, pathologic, and immunohistochemical features of ten cases of primary intrapulmonary meningioma were reviewed.

RESULTS

The patients were 4 women and 6 men between the ages of 30 and 72 years (mean age: 51 years). In nine patients, the lung tumor was found during a routine chest radiographic study. The only patient with clinical symptomatology was a man who presented with a persistent cough of 45 days' duration. None of the patients had a previous history of central nervous system (CNS) meningioma or other tumor at the time of diagnosis. Macroscopically, the neoplasms were described as soft, white, well circumscribed lesions that ranged in size from 1.5 cm to 4 cm in greatest dimension. No predilection for any particular lobe or segment of lung was observed. Histologically, all the tumors showed the characteristic growth pattern of CNS meningiomas and were classified accordingly. Seven tumors were transitional meningiomas, and three were fibrous meningiomas. Psammoma bodies were observed in 50% of the tumors. Immunohistochemically, six cases showed positive staining for Epithelial Membrane Antigen (EMA) and vimentin, whereas two of these cases also showed focal positive staining for CD34. Clinical follow-up ranging from 1 month to 24 years was obtained for 6 patients. All the patients were alive and well except for 1 female who died 20 years after the initial diagnosis at age 92 of a cerebrovascular accident.

CONCLUSIONS

The clinical follow-up in this study suggests that these tumors are amenable to surgical resection, and when the tumor is resected in its entirety, the patient is cured. In addition, the immunohistochemical results suggest that, as in CNS meningiomas, EMA and vimentin are the most reliable immunologic markers for these tumors.

Pleomorphic (giant and spindle cell) carcinoma is genetically distinct from adenocarcinoma and squamous cell carcinoma by K-ras-2 and p53 analysis

Pleomorphic carcinoma (PC) of lung is a poorly differentiated epithelial neoplasm predominantly composed of pleomorphic giant and/or spindle tumor cells. The WHO classification of lung cancer recognizes spindle cell carcinoma and giant cell carcinoma as separate neoplasms related to squamous cell carcinoma (SqC) and large cell carcinomas, respectively. Further, the presence of foci of SqC or adenocarcinoma (AdC) in, respectively, 10% and 45% of PC produces additional uncertainty as to the distinctive nature of this tumor type. In this study, the authors tested the hypothesis that PC is an entity separate from SqC or AdC by evaluating the mutational spectrum seen in these tumor types. This is performed by documenting and comparing mutation type and rate of K-ras-2 and p53 genes in PC, SqC, and AdC. Comparative DNA sequence and immunohistochemical analysis were performed on 22 PC, 42 SqC, and 97 AdC. Archival formalin-fixed, paraffin-embedded tissues formed the basis of the study. Immunohistochemical staining with p53 antibody (DO-7) revealed statistically significant differences in the intensity and frequency of staining of PC (weak, 86% of cases) versus SqC (strong, 52% of cases) and AdC (strong, 27% of cases) (P < .001). Topographic genotyping with subsequent polymerase chain reaction (PCR) and sequence analysis of K-ras-2 showed mutations in significantly fewer cases of PC (9%, 2 of 22 cases) than in AdC (36%, 35 of 97 cases) or SqC (0%, 0 of 42 cases) (P < .001). Pleomorphic carcinoma also showed significantly fewer p53 point mutations (14%, 3 of 22 cases) than did AdC (27%, 26 of 97 cases) of SqC (43%, 18 of 42 cases) (P < .01). Finally, the p53 mutations in PC were more common in exon 7, whereas those in SqC and AdC were more frequent in exon 8. These findings reveal significant differences in the pattern and frequency of genetic mutations between PC and pulmonary SqC and AdC and are in keeping with the separate histopathologic classification of these tumors.

Primary mediastinal and testicular seminomas: a comparison of K-ras-2 gene sequence and p53 immunoperoxidase analysis of 26 cases

Primary mediastinal seminomas (MS) are rare tumors. Histologically, they are similar to their counterpart in the gonads. The survival rate has varied from 50% to 85% in different series. However, large series of these tumors primarily in the mediastinum are lacking. At the molecular level, a few reports document K-ras mutations in up to 40% of testicular seminomas (TS), localized predominantly to codon 12. Reports on TS p53 immunohistochemistry (IHC) range from negative to overexpression approaching 90% of cases, and by sequence analysis one small series showed a 23% mutation rate. To date, no analyses have been performed for either K-ras mutations or p53 immunohistochemical expression in primary MS. The authors studied 13 cases each of primary MS and TS from archival formalin-fixed, paraffin-embedded sections in which adequate tumor sampling and clinical history, including serological studies, and histological, histochemical, and IHC staining, were performed to confirm the diagnosis. p53 immunoperoxidase staining using citrate buffer/microwave antigen retrieval was performed. Topographic genotyping was performed on 5-microns-thick tissue sections up to 17 years old, in which the neoplastic cell population was sampled. Additionally, multiple sites within a given cases were sampled to determine clonality of the tumor cell population. Polymerase chain reaction and subsequent sequence analysis of the K-ras-2 exon-1 gene was used for mutation analysis. Focal weak staining with p53 IHC was observed in 4 of 13 (31%) MS and 10 of 13 (77%) TS cases, with all remaining cases being negative (P < .05). Only one MS case (8%) showed K-ras mutation (codon 13 GGC > GAC; glycine > aspartate), which is in contrast to 2 of the TS cases (15%), showing codon 12 mutations. All the remaining cases were wild type. Therefore, primary mediastinal seminomas appear to be different in their K-ras sequence and p53 immunostain profile from TS. Codon mutation type may be useful in determining primary versus metastatic origin of a mediastinal seminoma.

Pleomorphic large cell lymphomas of the mediastinum

Nine cases of primary non-lymphoblastic, non-Hodgkin's large cell lymphomas of the mediastinum characterized by a highly pleomorphic histologic appearance are described. The patients, four women and five men, were aged 30 to 65 years. All patients presented with symptoms referable to their tumors, including cough, chest pain, dyspnea, pleural effusion, and superior vena cava syndrome. Clinical and pathologic staging in all patients showed that the bulk of the tumor was confined to the chest cavity at the time of initial diagnosis, with local infiltration into the neck, lung hilum, and surrounding mediastinal structures. Three different histological growth patterns were observed: one composed of a diffuse proliferation of pleomorphic, highly atypical cells with bizarre nuclear features that closely resembled a high grade sarcoma; another one composed of sheets of large, epithelial-appearing atypical cells suggestive of anaplastic carcinoma; and another pattern characterized by a pleomorphic proliferation of large lymphoid cells admixed with numerous scattered Reed-Sternberg-like cells reminiscent of the lymphocyte-depleted variant of Hodgkin's disease. Immunohistochemical studies on paraffin-embedded tissue sections in all cases showed positive staining of the tumor cells with CD20 and CD45 antibodies and negative staining with a large panel of markers, including broad-spectrum keratin, CAM 5.2, carcinoembryonic antigen, epithelial membrane antigen, vimentin, actin, desmin, HMB 45, S-100 protein, CD3, CD15, CD30, and CD45RO. Because of their location restricted to the anterior mediastinum, frequent lack of recognizable lymph node architecture, and bizarre cytologic features, the present group of lesions posed difficulties for diagnosis, their correct identification was achieved through the application of a panel of immunohistochemical markers. An awareness of these unusual histologic appearances of primary large cell lymphoma in the mediastinum and inclusion of a broad panel of lymphoid markers are therefore recommended for the evaluation of pleomorphic, undifferentiated malignant neoplasms of this anatomic region.

Chordomas of the mediastinum: clinicopathologic, immunohistochemical, and ultrastructural study of six cases presenting as posterior mediastinal masses

Six cases of chordomas presenting as primary posterior mediastinal tumors are described. Three patients were female, and three were male between the ages of 8 and 65 years (mean, 40.6 years). In all cases, the tumors presented radiographically as relatively well-circumscribed, encapsulated soft tissue masses that did not seem to be related to the thoracic or dorsal spine. Only in one case, focal infiltration of bone at the level of T6-T7 was observed at the time of surgery. Histologically, the lesions showed a spectrum of features that ranged from sheets and cords of large cells with abundant vacuolated cytoplasm to small, stellate cells embedded within an abundant mucoid matrix. In one case, the cell population showed more pronounced nuclear atypia with loss of cytoplasmic vacuolization, frequent mitotic figures, necrosis, and solid areas characterized by a perivascular distribution of atypical spindle cells set against a myxoid stroma. Another case showed features of chondroid chordoma, with an immature chondroid-appearing matrix surrounding the atypical tumor cells. Immunohistochemical studies in all cases showed positive staining of the tumor cells with CAM 5.2 and broad-spectrum keratin, epithelial membrane antigen (EMA) and vimentin, and, to a lesser extent, with S-100 protein. Stains for muscle actin, carcinoembryonic antigen (CEA), and desmin were negative. Ultrastructural examination in two cases showed a spectrum of features that varied from large cells with abundant cytoplasm containing scattered ribosomes, glycogen granules, Golgi apparatti, abundant intermediate filaments, and small lumen formation with immature microvilli to smaller cells with elongated cytoplasmic processes, fewer intermediate filaments, rare desmosome type intercellular junctions, and complexes of mitochondria/rough endoplasmic reticulum. On clinical follow-up, two patients died with metastases to the lungs, chest wall, and liver from 1 to 3 years after diagnosis, and two patients are alive and well without evidence of disease after 3 and 16 years. Chordoma should be entertained in the differential diagnosis of posterior mediastinal tumors. Application of immunohistochemical stains or electron microscopy will be of aid in separating them from other conditions that may histologically closely resemble these lesions.

Thymic carcinoid with prominent mucinous stroma. Report of a distinctive morphologic variant of thymic neuroendocrine neoplasm

Four cases are described of a distinctive morphologic variant of thymic carcinoid that was characterized by abundant stromal mucin admixed with the neuroendocrine elements resulting in a histologic picture reminiscent of metastatic mucin-secreting carcinoma. The patients were three men and a woman, aged 22 to 43 years. The tumors presented with symptoms of chest discomfort, cough, and dyspnea and were described as large anterior mediastinal masses on chest radiographs and computerized scans. Histologically, all cases showed nests and strands of tumor cells embedded in an abundant lightly eosinophilic, mucinous stroma with small cellular clusters as well as scattered single tumor cells seen floating in the mucin. The mucinous matrix was negative for periodic acid Schiff's and mucicarmine stains; alcian blue stains at pH 2.5 showed strong positivity of the mucinous material; this reaction was abolished by treatment with hyaluronidase, indicating the presence of nonepithelial stromal mucosubstances. Immunohistochemical stains showed strong positivity of the tumor cells with CAM 5.2, chromogranin, synaptophysin, and neuron-specific enolase, and negative staining with carcinoembyronic antigen and epithelial membrane antigen. Electron microscopy done in one case showed abundant dense-core cytoplasmic neurosecretory granules; there was no evidence of glandular secretory activity by the tumor cells. The tumors in two patients behaved in a highly aggressive fashion, with invasion of the chest wall, recurrence, and metastases to the lungs, pleura, and axillary, retroperitoneal, and mesenteric lymph nodes. Thymic carcinoid should be considered in the differential diagnosis of mediastinal neoplasms displaying prominent mucinous features. Application of immunostains and electron microscopy will be of value for establishing the correct diagnosis in this setting.

Solitary fibrous tumors of soft tissue. A clinicopathologic and immunohistochemical study of 12 cases

We describe 12 cases of primary soft tissue neoplasms that showed the histologic and immunohistochemical features of solitary fibrous tumors of serosal surfaces (solitary fibrous mesothelioma, submesothelial fibroma). Nine patients were women and three were men whose ages ranged from 28 to 83 years. Seven lesions were located in the head and neck region, and the remainder were located in the back, buttock, perineum, and groin. The lesions measured from 1 to 6 cm in greatest diameter and presented grossly as well-circumscribed, unencapsulated, soft to rubbery tissue masses. Histologically they were characterized by a proliferation of spindle cells exhibiting a variety of growth patterns, including storiform, herringbone, neural with wavy nuclei, and hemangiopericytic admixed with areas of sclerosis. In two cases the lesions showed areas of increased cellularity with occasionally scattered mitotic figures. Three cases were located adjacent to a major salivary gland; in one, entrapment of normal salivary gland acini and ducts could be observed at the edges of the lesion. Immunohistochemical studies showed positive staining of the spindle cells with CD34 (anti-HPCA-1) and vimentin antibodies and negative staining with keratin, actin, desmin, S-100 protein, collagen type IV, and factor VIII related antigen. Follow-up from 6 months to 12 years has shown no evidence of recurrence or metastasis in any of our patients. Solitary fibrous tumors appear to represent ubiquitous mesenchymal neoplasms that may not be necessarily restricted to serosal surfaces. Identification of these lesions is of importance to avoid misdiagnosis with other more aggressive conditions in soft tissue locations.

Mediastinal seminomas with prominent cystic changes. A clinicopathologic study of 10 cases

We present 10 cases of thymic seminomas associated with prominent cystic changes. All patients were males, aged 16 to 79 years (median, 23.5). Clinically, two patients presented with chest pain/four were asymptomatic and the tumors were discovered on routine chest radiographs; one tumor was discovered incidentally at autopsy; and in three patients no clinical information was obtained. Grossly, the tumors were described as multilocular cystic lesions that ranged in size from 7 to 19 cm in greatest dimension, showing small focal areas of induration within the cyst walls. Histologically, the lesions were characterized by cystic spaces lined by squamous or cuboidal epithelium showing severe chronic inflammatory changes with areas of cholesterol cleft granulomas, lymphoid follicular hyperplasia, and scattered foci of residual thymic parenchyma within the walls of the cysts, resulting in a picture indistinguishable from acquired multilocular thymic cysts. Careful examination, however, revealed microscopic foci composed of a neoplastic proliferation of large polygonal cells with slightly eosinophilic to clear cytoplasm and large nuclei with prominent nucleoli. The atypical cells were admixed with an inflammatory background and were often accompanied by a florid granulomatous reaction. Periodic acid-Schiff histochemical reaction with diastase revealed moderate amounts of glycogen within the cytoplasm of the tumor cells. Immunohistochemical studies in five cases showed positive labeling of the tumor cells with placental alkaline phosphatase. Nine patients were treated by complete surgical excision of the mass, and additional postoperative radiation therapy was given to two patients. Follow-up information available for five patients showed all to be alive and well from 2 to 19 years after diagnosis (mean follow-up, 9 years). Four of the patients were lost to follow-up. The pathogenesis of the cystic process in these cases remained unsettled but may represent a reactive change secondary to epithelial hyperplasia of thymic epithelium. Thymic seminoma should be considered in the differential diagnosis of cystic lesions of the anterior mediastinum; extensive sampling of such lesions is therefore recommended for proper evaluation.

Outcomes of cochlear implants for New Zealand children and their families

Six children with multichannel cochlear implants and their families were evaluated by means of multiple measures to determine the impact of the cochlear implant on the child's speech perception, language, communication mode, and behavior and on the parents' stress levels. The children showed quite variable improvements in speech perception with the implant. One child showed marked improvements in language 6 months after implantation. Two of the children had behavior problems preimplantation that showed some improvement after implantation. Parenting stress was very high in some families, but on average, stress was lower and social support networks were more extensive than those previously reported in studies of parents of deaf children in the United States.

Smooth muscle tumours presenting as pleural neoplasms

Five smooth muscle tumours presenting as pleural neoplasma are presented. The patients were three women and two men aged between 21 and 69 years (mean = 45 years). Clinically, one patient presented with chest pain, one with empyema and the other three were asymptomatic. Two of the tumours were located in the left side of the chest cavity and three in the right side. In four cases, the lesions presented as solitary pleural-based masses that varied in size from 10-18 cm in greatest dimension: in two of these cases, involvement of the diaphragm was present in addition to the pleural involvement. In one case, the tumour was seen to totally encase the right lung simulating the growth pattern of malignant mesothelioma. Histologically, three cases displayed an atypical spindle cell proliferation with marked cellular pleomorphism, mitoses and areas of hemorrhage and necrosis. The other two cases were characterized by a bland-appearing smooth muscle proliferation of uncertain malignant potential composed of elongated cells with a moderate amount of eosinophilic cytoplasm and cigar-shaped nuclei, lacking significant nuclear pleomorphism or mitotic activity. Immunohistochemical studies showed strong positivity for alpha-smooth muscle actin in all cases, and for desmin in four of five cases, and a focal positive reaction for keratin in one case. Ultrastructural examination in one of the high-grade tumours showed features of smooth muscle differentiation. Three of the patients were treated by complete surgical excision while, in the other two patients, the lesions were incompletely resected.(ABSTRACT TRUNCATED AT 250 WORDS)

Thymolipoma: clinicopathologic review of 33 cases

The clinical, radiologic, and pathologic features of 33 cases of mediastinal thymolipoma are presented. The patients' ages ranged from 2 to 64 (mean, 33) years; 18 were male and 15 were female. Clinically, the majority of patients (18 cases) were asymptomatic. Five patients presented with upper respiratory symptoms, two patients presented with chest pain, two patients with myasthenia gravis, and one patient with a neck mass; no clinical information was available in four patients. All the tumors were located in the anterior mediastinum and in all cases complete surgical resection of the mass was accomplished. Radiographically, 20 cases showed an anterior mediastinal tumor; when available, computed tomography and/or magnetic resonance imaging demonstrated a mixture of fat and soft tissue elements in these tumors. Grossly, the tumors were described as fairly well-circumscribed, soft, yellowish, fatty tumors with focal solid areas. The tumors varied in size from 4.5 to 36 cm in greatest dimension. Histologically, they were characterized by the presence of abundant mature adipose tissue admixed with areas containing remnants of thymic tissue. The fatty tissue consisted of mature adipocytes devoid of atypia, and the thymic tissue component varied from strands of atrophic thymic epithelium to large areas containing thymic parenchyma showing the typical mixed epithelial/lymphocytic architecture with numerous Hassall's corpuscles. Areas of calcification and cystic degeneration of Hassall's corpuscles were quite prominent in a large number of cases. Our study shows that thymolipomas span the age ranges from the very young to adult individuals with a slight prevalence for patients under the age of 40.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary pulmonary rhabdomyosarcomas: a clinicopathologic and immunohistochemical study of three cases

Three cases of primary pulmonary rhabdomyosarcoma in adults are presented. The patients were all men between the ages of 57 and 78 yr (mean 67.5). All patients presented with symptoms referable to their tumors, including cough, shortness of breath, pleuritic chest pain, and weight loss. In one patient, a history of tobacco and alcohol abuse was obtained. Anatomically, two tumors were located in the left upper lobe and one in the left lower lobe. Grossly, the tumors ranged in size from 6 to 11.5 cm and were tan-gray, firm masses with areas of necrosis and hemorrhage. Histologically, the tumors were characterized by a spindle cell proliferation admixed with areas showing a pleomorphic cell population with numerous rhabdomyoblasts and areas of hemorrhage and necrosis. Immunohistochemically, all three tumors showed strong positivity with desmin and myoglobin antibodies and negative staining with antibodies against keratin, epithelial membrane antigen, and S-100 protein. All patients had a fatal outcome. Two patients died a few days after admission with respiratory distress; the third one died 2 years after diagnosis with widely metastatic disease. Autopsy findings in all cases disclosed disseminated metastases to multiple abdominal and thoracic organs. Primary pulmonary rhabdomyosarcoma should be considered in the differential diagnosis of poorly differentiated pulmonary neoplasms in adults and should be distinguished from other primary and metastatic sarcomas.

Leprosy in five human immunodeficiency virus-infected patients

We present five cases of leprosy in five human immunodeficiency virus-positive individuals. The patients were five men between the ages of 18 and 45 years. The five patients presented with skin lesions; three patients with hypopigmented skin lesions, one with skin macules and a history of leprosy, and one with papular lesions. In one patient, there was bilateral "claw hands." Histologically, two cases were categorized as lepromatous leprosy, two as borderline tuberculoid, and one as borderline lepromatous. Follow-up information obtained in the five patients showed one patient had died, and the remaining four patients were alive and receiving antileprosy treatment.

Liposarcoma of the anterior mediastinum and thymus. A clinicopathologic study of 28 cases

We studied 28 cases of anterior mediastinal liposarcoma occurring in 16 males and 12 females with a mean age of 43 years (range, 14-72). Presenting symptoms included dyspnea (four cases) and chest pain (four cases), although 11 tumors were detected incidentally by routine chest radiography. Seven cases were believed to be located within the thymus. Most (i.e., 25) of the cases were of low grade, with the well-differentiated lipoma-like or sclerosing subtypes constituting 60% and the myxoid subtype constituting 28%; the remaining 12% exhibited mixed features. Three cases were pleomorphic type. Several low-grade tumors exhibited widespread, dense aggregates of mature-appearing lymphocytes and plasma cells, which occasionally obscured the mesenchymal nature of the neoplasm, suggesting instead a lymphoid neoplasm or a reactive fibroinflammatory condition. The three high-grade tumors showed combinations of pleomorphic and round cell patterns, with focal myxoid areas. Of the cases grossly arising within the thymus, only one showed extensive thymic tissue within the lesion ("thymoliposarcoma"); six others exhibited residual thymus peripheral to the tumor. Clinical follow-up in 23 cases revealed recurrence in seven patients (31.8%), with a mean interval to recurrence of 3 years. Eight patients died (mean survival, 2.6 years), one postoperatively and three following a recurrence. Fifteen patients were alive (mean survival, 2 years), four with recurrent tumor. The myxoid tumors had a somewhat more aggressive course than the well-differentiated tumors. Metastases were not observed in any of the patients.

Mucoepidermoid carcinomas of the thymus. A clinicopathologic study of six cases

Six cases of mucoepidermoid carcinoma of the thymus are presented. The patients were two men and four women aged 17 to 66 years (median age, 34.5). Clinically, three patients had symptoms of chest discomfort and three were asymptomatic. Grossly, the tumors in three patients were described as cystic structures varying in size from 7 to 8 cm in greatest dimension, with focal areas of induration within the walls of the cyst that averaged from 1.5 to 3 cm. The other three cases had grossly and radiographically well-circumscribed, homogeneous tumor masses. Histologically, the lesions showed a spectrum of features that ranged from those of well-differentiated, to moderately well-differentiated, to poorly differentiated mucoepidermoid carcinoma, with sheets and solid islands of squamoid cells admixed with mucin-secreting epithelium lining gland-like spaces. In four cases, the tumor was histologically seen in continuity with the epithelial lining of multilocular cystic structures; the nonneoplastic components of the cysts contained abundant inflammation and showed the features of otherwise conventional acquired multilocular thymic cysts. Clinical follow-up showed that the two patients with intermediate and high-grade tumors died within 2 and 7 months after initial diagnosis. One of these patients showed at autopsy residual tumor limited to the mediastinum, whereas the other patient died with metastases to pericardium and myocardium despite postoperative radiation therapy. Two patients with low-grade tumors were alive and well with no residual disease 2 and 3 years after surgery, and the other two were lost to follow-up. Mucoepidermoid carcinoma of the thymus should be included in the differential diagnosis of cystic neoplasms of the thymus. As with their counterparts at other sites, the biologic behavior of these tumors closely correlates with their degree of differentiation and amount of cytologic atypia.

Primary pulmonary sarcomas with features of monophasic synovial sarcoma: a clinicopathological, immunohistochemical, and ultrastructural study of 25 cases

We present 25 cases of a primary pulmonary sarcoma bearing histological, immunohistochemical, and ultrastructural features indistinguishable from those of monophasic synovial sarcoma of soft tissue. The patients were 11 men and 14 women between the ages of 16 and 77 years. Clinically, the most common symptoms were chest pain, cough, shortness of breath, and hemoptysis. The lesions involved all lung segments. Grossly, they varied in size from 0.6 to 20 cm and were described as soft to rubbery tumors with areas of necrosis and hemorrhage, some with cystic changes. Two lesions involved the bronchial wall and in one case the tumor was described as encircling the bronchial tree. Histologically, all of the lesions were characterized by an atypical spindle cell proliferation with a solid growth pattern. Areas of myxoid, neural, hemangiopericytic, and epithelial-like growth pattern were observed. Mitoses, necrosis, and hemorrhage were seen in all lesions in varying proportions. Immunohistochemical studies for epithelial membrane antigen (EMA) and keratin showed strong focal positivity in 25 of 25 and 23 of 25 lesions, respectively. Immunohistochemical study for vimentin showed diffuse strong positivity in all lesions. Other immunostains, including desmin, smooth muscle actin, and S-100 protein, were negative. Electron microscopy in three cases showed spindle cells with elongated nuclei containing abundant cytoplasmic rough endoplasmic reticulum and well developed desmosome type intercellular junctions. Follow-up information ranging from 2 to 20 years was obtained in 18 patients. Six patients died of their tumors, whereas four patients died of unrelated causes without evidence of recurrence or metastases. Eight patients were alive with disease (recurrence and/or metastases) from 1 to 7 years after diagnosis. Four patients were alive and well without evidence of recurrence or metastases from 2 to 20 years (mean follow-up, 12.5 years). The present group of lesions appears to constitute a distinctive and as yet previously undescribed primary sarcoma of the lung, which probably represents the visceral counterpart of monophasic synovial sarcoma of soft tissue in a pulmonary location. Because of their distinctive biology these lesions should be distinguished from a variety of primary and metastatic malignancies of the lung.

Malignant mixed epithelial/mesenchymal neoplasms of the lung

The existence of biphasic neoplasms occurring primarily in the lung is a well-known albeit rare event. The spectrum of malignant tumors displaying a mixed epithelial/mesenchymal growth pattern is rather narrow when these tumors occur primarily in the lung. The two most often encountered neoplasms showing features of epithelial and mesenchymal differentiation are carcinosarcomas and pulmonary blastomas. Tumors with analogous features are of ubiquitous distribution in the human body and have been described in numerous other organs, including the gastrointestinal tract, the genitourinary tract, and the endocrine system. Although the histopathologic features of these tumors may seem simple in most cases, there appear to be numerous pitfalls in their diagnosis; gray areas still remain in the characterization of these tumors, because a certain degree of overlap may be encountered with these two conditions. Such problems are understandable because the incidence of these tumors in the general population is very rare. Therefore, one is expected to find divergent points of view regarding these neoplasms. It is of importance, however, to unify criteria not only for diagnostic purposes, but also to determine the prevalence and behavior of these neoplasms, because such information may provide a rationale for adjustment and improvement in the treatment and diagnosis of these unusual neoplasms. We will review past and current concepts regarding these unusual tumors, as well as their more salient histopathologic features.

Unusual manifestations of metastatic tumors to the lungs

Because of the lung's rich capillary bed and central location in the circulatory system, this organ is one of the most frequent recipient sites for metastatic spread of disease. The histopathologic diagnosis in the vast majority of cases is straightforward and usually supported by clinical findings and a prior history of a known primary tumor elsewhere. However, unusual circumstances may arise: a primary tumor may remain occult at the time of pulmonary metastases, the metastasis may develop after a long period of latency, or the histopathologic appearance of the metastasis may assume a form that is uncharacteristic or inconsistent with the suspected primary lesion, which raises the possibility of the emergence of a second primary tumor in the lung. Herein we review a variety of unusual manifestations of metastatic disease to the lungs that may pose difficulties for diagnosis and interpretation. Emphasis is made on the histological differential diagnosis and the clues that may alert the pathologist to recognizing the process as metastatic in origin.

Primary salivary gland-type tumors of the lung

Primary pulmonary neoplasms that bear similar histopathologic features to those seen in salivary glands are rare. Although their presence has been well documented in the literature, it has been primarily in the form of single case reports. Consequently, it has been difficult until recently to determine their prevalence, clinical behavior, treatment, and spectrum of histopathologic features. Moreover, because of the rarity with which these tumors occur, one needs to be familiar with their diverse histopathologic features to comfortably arrive at the correct diagnosis. Because of their close histological similarities to their salivary gland counterparts, careful clinical evaluation is necessary to establish the primary nature of these tumors in the lung and to rule out the possibility of a metastasis. Another feature that may generate difficulties in interpretation is that some of these tumors may share certain histopathologic and some immunohistochemical features with each other. This may pose a serious problem, particularly when dealing with small biopsy samples. Therefore, the use of special studies such as electron microscopy and routine histochemistry may be beneficial and must be used in addition to conventional microscopy and immunohistochemistry to corroborate the diagnosis. In essence, the diagnosis of these tumors requires a combined approach that must include a detailed clinical history, a reasonably sized sample for histopathologic evaluation, histochemical and immunohistochemical studies, and an ultrastructural examination.