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.

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.

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.

Squamoid eccrine ductal carcinoma

We describe three cases of a distinctive cutaneous adnexal neoplasm showing features of eccrine ductal differentiation that were characterized by a prominent squamoid component. The tumours presented as solitary dermal nodules on the head and neck areas and the extremities in elderly patients. Histologically, they were characterized by a prominent squamous proliferation with atypia, keratinous cyst formation and squamous eddies which seemed to merge with areas showing eccrine ductal differentiation, including ductular formations in continuity with eccrine ductal epithelium. Clinical follow-up in one case showed multiple local recurrences over a period of 3 years despite complete surgical excision. Squamoid eccrine ductal carcinoma should be considered in the differential diagnosis of cutaneous adnexal neoplasms showing squamoid and ductal features of differentiation.

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.

Cytokeratin 20 immunoreactivity distinguishes Merkel cell (primary cutaneous neuroendocrine) carcinomas and salivary gland small cell carcinomas from small cell carcinomas of various sites

Cytokeratin 20 (CK20) is a low-molecular-weight cytokeratin (CK) that shows restricted expression in the gastrointestinal epithelium, urothelium, and Merkel cell. Recent studies have suggested that since Merkel cell (primary cutaneous neuroendocrine) carcinomas are consistently CK20-positive, this feature may help to distinguish it from pulmonary small cell carcinomas. However, only limited numbers of these tumors have been studied, and the pattern of CK20 expression in other small cell carcinomas has not been established. Therefore, we studied CK20 expression in small cell carcinomas from a wide variety of sites. Immunohistochemical study was performed on paraffin sections using CK20 antibody, coupled with antigen retrieval by pressure cooking in citrate buffer. The cases included 34 Merkel cell carcinomas and 89 small cell carcinomas from various sites (pulmonary, 37; gastrointestinal tract, nine; pharynx and tongue, two; sinonasal tract, three; salivary gland, five; larynx, nine; breast, two; thymus, three; uterine cervix and corpus, 12, prostate, three; urinary bladder, two; kidney, one; pancreas, one). In addition, all cases were immunostained with pan-CK (MNF-116) and low-molecular-weight CK (CAM5.2) antibodies to ascertain their epithelial nature. With the exception of one case, all Merkel cell carcinomas were CK20-positive; and 30 of the 33 cases showed a punctate pattern. Almost 100% of tumor cells were positive, except for two cases that showed staining of 10% and 30% of tumor cells, respectively. Among the other small cell carcinomas, only five cases were CK20-positive, including one of 37 pulmonary (40% cells positive in punctate pattern), one of 11 cervical (10% cells positive), and three of five salivary gland (100% cells positive). We conclude that CK20-positivity in a small cell carcinoma of uncertain origin strongly predicts a diagnosis of Merkel cell carcinoma, especially if the majority of tumor cells are positive. A negative CK20 reaction can practically rule out Merkel cell carcinoma, provided that an effective antigen retrieval technique is used and appropriate staining is obtained with other cytokeratin antibodies. The frequent CK20 positivity observed in salivary gland small cell carcinomas in this series suggests that at least some of them may be more closely related biologically to Merkel cell carcinoma than to pulmonary-type small cell carcinoma. This may explain why they are far less clinically aggressive than other small cell carcinomas.

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.

Immunoreactivity for the human hematopoietic progenitor cell antigen (CD34) in lipomatous tumors

The human hematopoietic progenitor cell antigen (CD34) recently was shown to react with a variety of nonhematopoietic tissues and their tumors, including vascular endothelium, dendritic interstitial fibroblastic cells, and endoneurial cells as well as with the neoplastic cells in a variety of mesenchymal neoplasms of unknown etiology, such as Kaposi's sarcoma, dermatofibrosarcoma protuberans, epithelioid sarcoma, gastrointestinal stromal tumors, and solitary fibrous tumors. Additionally, it has been claimed that normal adipocytes may also react with this antibody. We studied a series of 90 lipomatous lesions to examine the pattern of immunoreactivity of the CD34 antigen in adipose tissue neoplasms. The study included 14 lipomas, 19 angiolipomas, 4 atypical lipomas, 18 spindle cell lipomas, 3 renal angiomyolipomas, 1 intramuscular lipoma, and 31 liposarcomas. Immunostains identified a network of CD34+ spindle cells admixed with the adipose tissue elements in all cases of lipoma, angiolipoma, angiomyolipoma, intramuscular lipoma, and well-differentiated lipoma-like liposarcoma. Additionally, the spindle cell component in all cases of spindle cell lipoma were strongly positive for this antigen. Atypical, stellate spindle cells and multinucleated "floret" cells in all cases of atypical lipoma as well as in six of 12 cases of well-differentiated lipoma-like liposarcoma of deep soft tissue were also positive for CD34. Scattered spindle cells in all cases of myxoid liposarcoma and in one case of round cell liposarcoma, as well as the sarcomatous component in one case of "dedifferentiated" liposarcoma, were strongly positive for this antigen. The round cells in myxoid liposarcoma and round cell liposarcoma, the signet-ring and multivacuolated lipoblasts in well-differentiated liposarcoma, and the pleomorphic atypical cells in pleomorphic liposarcoma were uniformly negative. The results of this study appear to indicate that lipomatous tumors may harbor a population of CD34+ interstitial dendritic spindle cells. Overgrowth or clonal expansion of this dendritic cell subpopulation may account for the development of spindle cell lipomas and for the spindle cell component in some cases of "dedifferentiated" liposarcoma.

Effect of colchiceine and ursodeoxycholic acid on hepatocyte and erythrocyte membranes and liver histology in experimentally induced carbon tetrachloride cirrhosis in rats

Colchiceine and ursodeoxycholic acid (UDCA) are drugs currently in use as therapy for different types of liver damage. We evaluated their ability to reverse the damage induced by carbon tetrachloride (CCl4) in rats. Six groups were analysed: (1) CCl4 (0.4 g kg(-1), i.p., three times a week) for 13 weeks; (2) CCl4 for 8 weeks followed by colchiceine (60 microg kg(-1)) + CCl4 for 5 weeks; (3) CCl4 for 8 weeks and thereafter UDCA (25 mg kg(-1)) + CCl4 for 5 weeks. Groups 4, 5 and 6 were appropriate controls of colchiceine, UDCA and vehicles respectively. Na+,K+- and Ca2+-ATPase activities and the cholesterol-phospholipid (CH/PL) ratio from erythrocyte and hepatocyte membranes were quantified. Membrane enzymatic activities and CH/PL ratios were affected more in group 1 than groups 2 and 3. We concluded that colchiceine and UDCA were effective drugs in this model of liver damage.

The oncocytic variant of papillary carcinoma of the thyroid: a clinicopathologic study of 15 cases

The oncocytic variant of papillary carcinoma of the thyroid represents an unusual neoplasm whose clinicopathological features and biological behavior have not been thoroughly characterized. We studied 15 cases of thyroid tumors predominantly composed of oncocytic (oxyphilic) cells that were characterized by showing the classical nuclear features of papillary carcinoma of the thyroid. Thirteen patients were women, and two were men; their ages ranged from 34 to 86 years. The tumors measured from 1 to 4 cm in diameter and were well circumscribed and confined to the thyroid gland in all cases except for one, in whom there was extrathyroidal local extension. Histologically, all tumors showed, at least focally, the formation of papillary structures; in 13 cases the papillary features were found to predominate or were admixed in equal proportion with a follicular pattern of growth, and in two the follicular growth pattern predominated and only abortive, small papillary structures could be found on extensive search. In all cases, the classical optically clear nuclei of papillary carcinoma were present throughout the lesions. Nuclear grooves and intranuclear cytoplasmic inclusions were also a prominent and constant component of these lesions. In 13 cases, the tumors showed the features of Hashimoto's or lymphocytic thyroiditis in the surrounding, uninvolved thyroid parenchyma. Follow-up of 1.2 to 13 years (median, 4.5 years) showed the development of cervical lymph node metastases 9 months after surgery in one case; the remainder of patients were alive and free of disease. Oncocytic papillary carcinoma seems to represent a distinctive morphological variant of carcinoma of the thyroid that in our experience does not appear to behave more aggressively than conventional papillary carcinoma. The frequent association of these tumors with autoimmune thyroiditis raises the possibility that the oncocytic changes may be pathogenetically related with the latter process. These tumors should be distinguished from benign and malignant Hurthle cell tumors and other oncocytic thyroid neoplasms that may follow a different biological behavior.

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.

Gastrointestinal stromal tumors

Stromal tumors of the gastrointestinal tract represent relatively rare lesions that are thought to arise from connective tissue elements located along the entire length of the gut. For many years these tumors have been the subject of much controversy and debate in the literature regarding their histogenesis, criteria for diagnosis, prognostic features, and nomenclature. Only a minority of these lesions, mainly those confined to the esophagus and rectum, have been shown to correspond to mature, well-differentiated types of neoplasms such as leiomyoma or leiomyosarcoma of the conventional type. The majority of stromal tumors of the gastrointestinal tract correspond to a heterogeneous group of lesions that have as their common denominator an immature proliferation of epithelioid or spindle cells arising from its muscle layer and showing partial or incomplete myoid, neural, ganglionic, or mixed features of differentiation. This review will attempt to summarize our current knowledge and understanding of these lesions based on review of the literature and the author's personal experience, with an analysis of the criteria for distinguishing between benign and malignant tumors, and a proposal for a working classification for these lesions.

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.

Gastrointestinal stromal tumors with prominent signet-ring cell features

Three cases of gastrointestinal stromal tumors characterized by a population of cells displaying prominent signet-ring cell features are described. The tumors occurred in women aged 45 to 74 years and presented as small (< 2.5 cm), well-circumscribed, serosal nodules located within the wall of the stomach, small bowel, and rectum. Histologically, the lesions were characterized by a proliferation of large, round-to-oval cells containing abundant clear cytoplasm with displacement of the nuclei toward the periphery, which imparted to them a striking signet-ring cell configuration. In some areas, the signet-ring cells were seen to merge with short fascicles of spindle cells, whereas in other areas, the tumor cells were associated with prominent deposition of myxoid matrix. Histochemical studies showed glycogen granules within the cytoplasm of the tumor cells in two cases. Immunohistochemical studies showed a heterogeneous pattern of staining, with strong positivity for actin, vimentin, and CD34 in one case; strong vimentin and S-100 protein and weak, focal positivity for actin and CD34 in another; and vimentin positivity alone in the third. The present cases illustrate an unusual morphologic appearance of gastrointestinal stromal tumors that should be distinguished from primary and metastatic mucin-secreting carcinoma and other types of neoplasms with clear cell or signet-ring cell features.

Microglandular carcinoma of the pancreas: immunohistochemical and ultrastructural study of an unusual variant of pancreatic carcinoma that may closely resemble a neuroendocrine neoplasm

Two cases are described of an unusual form of primary adenocarcinoma of the pancreas characterized histologically by their striking resemblance with a neuroendocrine neoplasm. The tumors were composed of a population of relatively small, uniform cells arranged in sheets admixed with small microglandular structures resulting in a cribriform pattern of growth. The tumor cells displayed scant cytoplasm with indistinct cell borders and round to oval nuclei with irregular clumping of chromatin and small, inconspicuous nucleoli. Immunohistochemical studies in both cases showed positivity of the neoplastic cells with CAM 5.2 antibodies and negative staining with a battery of neuroendocrine-related markers including chromogranin, NSE and synaptophysin, as well as with a variety of peptide hormones including insulin, glucagon, vasoactive intestinal polypeptide, gastrin and serotonin. Ultrastructural examination revealed a cohesive population of cells forming abortive glandular lumens lined by imperfectly formed microvilli and showing well-developed junctional complexes. No dense core neurosecretory granules or zymogen granules could be identified in any of the cells, supporting a ductal type of differentiation for these tumors. The main importance of recognizing this rare variant of pancreatic adenocarcinoma lies in avoiding misdiagnosis with other primary and metastatic neuroendocrine neoplasms of this organ. Immunohistochemical and ultrastructural examination will be of value in such cases for differential diagnosis.

Benign cutaneous adnexal tumors with combined folliculosebaceous, apocrine, and eccrine differentiation. Clinicopathologic and immunohistochemical study of eight cases

Benign cutaneous adnexal tumors displaying divergent differentiation are rare, with very few well-documented cases reported in the literature. We describe eight cases of benign adnexal tumors showing a variable combination of eccrine, apocrine, and folliculosebaceous differentiation. Clinically, all tumors presented as solitary, slowly enlarging dermal or subcutaneous nodules located in the head and neck and the extremities. Histologically, they were characterized by well-circumscribed, unencapsulated nodules composed of a lobular proliferation of epithelial cells displaying a spectrum of trichogenic, sebaceous, apocrine, and eccrine differentiation. The histological spectrum included lobules and trabeculae of basaloid cells with glandular and ductal elements, well-formed folliculosebaceous units, primitive follicles, and foci of tricholemmal keratinization. Immunohistochemical evaluation in four cases showed similar cytokeratin, carcinoembryonic antigen, and epithelial membrane antigen staining profiles as those reported for sweat gland adenomas; in addition, focal S-100 protein positivity and GCDFP-15 positivity could also be demonstrated, suggesting eccrine-apocrine differentiation. The tumors were most frequently confused histologically with other adnexal neoplasms, including sebaceoma, sebaceous adenoma, basal cell carcinoma, chondroid syringoma, and trichoepithelioma. The present series highlights the capability.

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.