Keratin proteins and carcinoembryonic antigen in synovial sarcomas: an immunohistochemical study of 24 cases

Pleural malignant mesothelioma versus pleuropulmonary synovial sarcoma: a clinicopathological study of 22 cases with molecular analysis and survival data

The aim of this study was to carry out a comparative analysis by transducin-like enhancer of split 1 (TLE1) immunohistochemistry and molecular analysis of SYT-SSX, for 16 pleural predominantly sarcomatoid mesotheliomas and six cases of pleuropulmonary synovial sarcoma (five pleural in distribution only, with one case of a predominantly subpleural upper lobe synovial sarcoma), all of which were solely or predominantly monophasic. Our comparison included survival and some clinical data. We consider that the following points emerged from this study.

Synovial Sarcoma With a Predominant Epithelial Component

A case of synovial sarcoma of the lower leg in a 59-year-old woman with a predomi nant epithelial component is reported. Histologically, the tumor showed a well-devel oped epithelial component with a sheet-like and cribriform pattern with a sparsely distributed spindle cell component. Immunohistochemically, the epithelial component was positive for cytokeratins and epithelial membrane antigen, while the spindle cell component was positive for cytokeratins, epithelial membrane antigen, and vimentin. The epithelial component of synovial sarcoma is indistinguishable from carcinoma morphologically and immunohistochemically, therefore the presence of a biphasic pattern, even with a paucity of spindle cell component, is a crucial finding to establish a diagnosis of synovial sarcoma. The recognition and subclassification of this type of synovial sarcoma is important in arriving at a correct prognosis. Int J Surg Pathol 1(4): 261-268, 1994

Utility of Immunohistochemistry in the Diagnosis of Pleuropulmonary and Mediastinal Cancers: A Review and Update

Context

Immunohistochemistry has become an indispensable ancillary tool for the accurate classification of pleuropulmonary and mediastinal neoplasms necessary for therapeutic decisions and predicting prognostic outcome in the era of personalized medicine. Diagnostic accuracy has significantly improved because of the continuous discoveries of tumor-associated biomarkers and the development of effective immunohistochemical panels.

Objective

To increase the accuracy of diagnosis and classify pleuropulmonary neoplasms through immunohistochemistry.

Data Sources

Literature review, authors' research data, and personal practice experience.

Conclusions

This review article has shown that appropriately selecting immunohistochemical panels enables pathologists to effectively diagnose most primary pleuropulmonary neoplasms and differentiate primary lung tumors from a variety of metastatic tumors to the lung. The discovery of new mutation-specific antibodies identifying a subset of specific gene-arranged lung tumors provides a promising alternative and cost-effective approach to molecular testing. Knowing the utilities and pitfalls of each tumor-associated biomarker is essential to avoiding potential diagnostic errors.

Use of p40 and p63 immunohistochemistry and human papillomavirus testing as ancillary tools for the recognition of head and neck sarcomatoid carcinoma and its distinction from benign and malignant mesenchymal processes

Sarcomatoid carcinoma (SC) is a variant of head and neck squamous cell carcinoma characterized by a prominent and sometimes exclusive spindle cell component. Distinction from a sarcoma or reactive stroma can be problematic, particularly in cases in which the conventional component is not obvious. The value of immunohistochemistry is limited because of the loss of cytokeratin expression in a sizable percentage of cases. Staining for p63 can enhance detection of epithelial differentiation, but its usefulness is offset by expression in various soft tissue proliferations. Staining for p40--a squamous-specific isoform of p63--could potentially improve diagnostic accuracy. Immunohistochemistry for pancytokeratin, p63, and p40 was performed on 37 head and neck SCs, 201 soft tissue neoplasms, and 40 reactive stromal proliferations. The SCs were also stained for p16 in the event that some of the tumors were human papillomavirus (HPV) related. HPV in situ hybridization was performed on p16-positive cases. Twenty-three of 37 (62%) SCs were positive for pancytokeratin, 23 of 37 (62%) were positive for p63, and 20 of 37 (54%) were positive for p40. Compared with p63, p40 staining was less likely to be observed in soft tissue tumors (5% vs. 30%) and reactive stromal proliferations (0% vs. 30%). HPV16 was detected in 3 of 10 (30%) SCs of the oropharynx but in none of the nonoropharyngeal SCs. p40 staining does not improve the sensitivity for diagnosing SC, but it does diminish the risk of misdiagnosing a sarcoma or reactive stroma as SC. The presence of a sarcomatoid variant of HPV-related oropharyngeal cancer points to HPV testing as a useful diagnostic tool for atypical spindle cell proliferations of the oropharynx.

Biphasic synovial sarcoma of the abdominal wall

Synovial sarcoma arising in the abdominal wall is a rare tumor. We report a case of a 38-year-old man who complained of abdominal pain. Physical examination revealed a firm mobile mass, 25 cm in diameter, in the left lower abdominal wall. The tumor was first thought to be a sarcoma arising from the omentum or mesentery. During surgery, a large tumor was found attached to the inner surface of the abdominal wall and compressing the gastrointestinal tract. On microscopic examination the tumor corresponded to a biphasic synovial sarcoma immunoreactive for cytokeratins (AE1/AE3, 7 and 19), epithelial membrane antigen and carcinoembryonic antigen in the epithelial tumor cells, for E-cadherin especially in their glandular structure, vimentin, CD99, and CD56 in the spindle cell component and for bcl-2 protein. The tumor recurred at the same site, and clinical course progressed to death 3 months after the initial diagnosis.

Primary synovial sarcoma of the lung

A 45 -year-old woman presented chest pain and a well-defined oval shaped mass on a chest radiograph. A malignant pulmonary tumor was suspected and a right pneumonectomy was performed. The tumor measured about 13 x 12 cm, was pale-yellow in color and soft in texture. Histologically, it had round to oval and spindle-shaped cells with minimal cytoplasm, hyperchromatic nuclei, inconspicuous mitoses and only slight fibrous stroma. Immunohistochemically, the tumor cells were positive for vimentin, CD 99, BCL-2 protein and EMA. The reverse transcriptase-polymerase chain reaction (RT-PCR), using RNA extracted from fresh-frozen tissue, demonstrated SYT/SSX-2 fusion transcripts, confirming the diagnosis of synovial sarcoma.

Primary Synovial Sarcomas of the Mediastinum

A series of 15 cases of primary mediastinal neoplasms displaying histopathologic, immunohistochemical, and ultrastructural features of synovial sarcoma is presented. The patients' ages ranged from 3 to 83 years, with a male-to-female ratio of 2:1. Nine cases presented as anterior mediastinal masses with chest pain, shortness of breath, and pleural effusion, and 6 cases were in paravertebral location in the posterior mediastinum and presented with neck or back pain and pleural effusion. The tumors measured from 5 to 20 cm in greatest diameter and showed a tan white, soft to rubbery cut surface with areas of hemorrhage and necrosis and foci of gelatinous material. Four cases showed areas of cystic degeneration. In 7 cases, the tumors were well circumscribed; in 6 cases, the tumors grossly invaded the pleura, pericardium, heart, great vessels, chest wall, rib, and vertebra. Histologically, 5 cases displayed a biphasic growth pattern, with well-formed glandular elements admixed with a monotonous spindle cell population. Ten cases were exclusively composed of a monotonous atypical spindle cell proliferation. Immunohistochemical studies showed focal positivity of the tumor cells for cytokeratin and/or epithelial membrane antigen, and strong positivity for vimentin and bcl-2 in the spindle cells in all cases studied (10 of 10). Eight cases also showed focal positivity for CD99. Electron microscopic examination in 5 cases showed oval to spindle tumor cells with closely apposed cell membranes, abundant cytoplasmic intermediate filaments and rough endoplasmic reticulum, and immature desmosome-type cell junctions. Ten patients were treated by complete surgical excision and two by partial excision followed by radiation therapy. In 4 patients, the tumors were inoperable and treated with radiation therapy only. Clinical follow-up was available in 5 patients and showed local recurrence with metastases to lung, lymph nodes, and epidural space from 1 to 3 years in 4 cases and liver metastases and death due to tumor after 6 month in 1 case. Synovial sarcoma should be considered in the differential diagnosis of biphasic and monophasic spindle cell neoplasms of the mediastinum.

Localized pleural malignant mesothelioma

The occurrence of pleural malignant mesothelioma (MM) is unusual and the cases that appear as a localized tumor are extremely rare. A case of localized pleural MM including immunohistochemical findings is presented. A 70-year-old man had an abnormal shadow found during a routine roentgenogram at an annual health checkup and was admitted to Toneyama National Hospital (Toyonaka, Osaka, Japan) for detailed examinations. Chest X-rays showed a 2 x 5 cm-sized nodule with relatively smooth margins in the right segment three. Computed tomography (CT) showed an extrapleural mass with a smooth surface and a thickened parietal pleura, and results of a biopsy performed under CT scanning yielded MM. Systematic examinations did not show any metastasis and the patient underwent surgery for removal of the mass. The resected tumor, measuring 3.2 x 3.1 cm, was firm, partially encapsulated, and irregularly shaped. Pathological examinations revealed that it consisted of large polygonal cells, partially showing myxoid patterns, which led to a diagnosis of localized pleural MM. Tumor recurrence was seen, and the duration between initial symptoms and death was 29 months. This case suggests that localized pleural MM has a high proliferative potential and aggressive course, and is considered an early stage of diffuse pleural MM.

Calponin and h-caldesmon expression in synovial sarcoma; the use of calponin in diagnosis

AIMS

To assess the frequency of expression and potential diagnostic utility of calponin and caldesmon in synovial sarcomas.

METHODS AND RESULTS

Immunohistochemistry with antibodies to calponin and h-caldesmon was undertaken in paraffin sections from 50 synovial sarcomas (19 biphasic and 31 monophasic, of which one biphasic and eight monophasic tumours had poorly differentiated areas), 10 each of malignant peripheral nerve sheath tumour (MPNST), solitary fibrous tumour (SFT), dermatofibrosarcoma (DFSP), Ewing's sarcoma (ES/PNET), and neuroblastoma, eight alveolar rhabdomyosarcomas, five adult fibrosarcomas and five carcinosarcomas. Nine of 19 biphasic synovial sarcomas were positive for calponin in spindle and glandular areas, nine in spindle cells only, and one in glands only. All monophasic synovial sarcomas and poorly differentiated areas expressed calponin; in monophasic tumours this was focally (29% of cases), moderately (39%), or diffusely (32%) positive and the poorly differentiated areas were usually moderately or diffusely positive. Four synovial sarcomas showed focal reactivity for h-caldesmon. Calponin was found in 4/10 MPNST, 7/10 SFT, 4/10 DFSP, 3/5 fibrosarcomas and the spindle component of the carcinosarcomas. H-caldesmon was weakly positive in 1/10 MPNST, 4/10 SFT, 0/10 DFSP, 0/5 fibrosarcomas and 1/5 carcinosarcomas (glands only). Both markers were negative in the other small round cell tumours.

CONCLUSIONS

Calponin can be used as an additional marker for synovial sarcoma. Its absence argues against the diagnosis. The presence of calponin might be useful in distinguishing poorly differentiated synovial sarcoma from other small round cell tumours. H-caldesmon is not helpful in diagnosis of synovial sarcoma.

Conventional hemangiopericytoma: modern analysis of outcome

BACKGROUND

Hemangiopericytoma (HPC) is a rare vascular tumor, and pathologic distinction from synovial sarcoma and solitary fibrous tumor is a significant problem due to shared histologic features. In the current report the authors defined the clinical behavior and prognosis for patients with HPC.

METHODS

Between July 1982 and February 1998, 62 patients with a diagnosis of primary, recurrent, or metastatic HPC were identified from a prospectively maintained database. The pathology of all cases for which material was available (57 cases) was re-reviewed for histologic confirmation of the HPC diagnosis. Using strict pathologic criteria, including immunohistochemistry and electron microscopy, tumors from 25 of 57 patients qualified for the diagnosis of conventional hemangiopericytoma; those tumors formed the basis of the current report. Survival was determined by the Kaplan-Meier method.

RESULTS

At the time of initial presentation, 19 patients had primary tumors, 3 had locally recurrent disease, and 3 had metastatic disease. The most frequent anatomic sites for HPC were the extremities, the pelvis, and the head and neck, accounting for 80% of the total cases. The median followup (n = 25) was 49 months (range, 1 to 160 months). The two and five year overall survival rates (n = 25) were 93% and 86% respectively. The disease-specific survival was 86% at last followup. Patients undergoing complete resection (n = 16) showed a 100% median survival at 60 months.

CONCLUSIONS

At present, complete tumor resection for patients with conventional HPC is recommended. However, considering the favorable outcome in this disease, the authors caution against performing operations that may potentially cause loss of function or are limb threatening.

Primary pleuropulmonary synovial sarcoma: reappraisal of a recently described anatomic subset

BACKGROUND

Primary pleuropulmonary synovial sarcoma (SS) is a rare neoplasm and a recently recognized anatomic subset. Its clinicopathologic attributes are not yet well defined.

METHODS

In this study, the clinical and histopathologic features of 12 SS arising in the lung and/or pleura were analyzed.

RESULTS

The neoplasms occurred in 7 men and 5 women, 20-72 years old (median, 31 years), were well circumscribed with a mean size of 7.2 cm, and involved either lung (9 cases), pleura (2 cases), or both (1 case). All the tumors were of monophasic type. Nine showed a classic spindle cell pattern, and three showed predominantly poorly differentiated features. All but one case showed at least focal positivity for epithelial membrane antigen (EMA), a finding characteristic of this tumor. The lack of EMA staining in one case, proven by electron microscopy to be SS, was attributed to the scarcity of material available for immunohistochemical stains. The diagnosis was proven cytogenetically in three cases. Within 2 years, local recurrence developed in 8 patients (75%), 3 of whom developed metastasis (25%). Five patients died of their disease within 2.5 years, 4 of them from uncontrolled local disease.

CONCLUSIONS

The authors conclude that pleuropulmonary SS, although rare, represents a distinct anatomic subset having pathologic features similar to those of its soft tissue counterpart. Its clinical behavior appears more aggressive, perhaps because of relatively later presentation combined with the difficulty in obtaining a wide surgical margin.

Expression of protein gene product 9.5 in epithelioid and conventional malignant peripheral nerve sheath tumors

CONTEXT

Due to the frequent lack of S100 protein expression in malignant peripheral nerve sheath tumors (MPNSTs), especially the epithelioid variant, these tumors are difficult to diagnose without the aid of electron microscopy or a clinical history of neurofibromatosis.

METHODS

Protein gene product 9.5 (PGP9.5), a broad neural marker, is expressed in nerve fibers and neurons of both the peripheral and central nervous systems. We compared its expression to that of S100 protein in 16 cases of MPNST. As controls, 6 monophasic synovial sarcomas, 9 leiomyosarcomas, and 5 dermatofibrosarcoma protuberans were included.

RESULTS

Expression of PGP9.5 was seen in 15 MPNSTs, with 3 to 4+ positivity in the majority of the cases. Ten cases, 2 epithelioid and 8 conventional MPNSTs, were reactive with PGP9.5, but were negative for S100 protein. Five cases were immunoreactive for both S100 protein and PGP9.5. One case was negative for PGP9.5 but demonstrated focal S100 protein positivity. Expression of PGP9.5 was seen in 4 of 6 synovial sarcomas, 3 of 9 leiomyosarcomas, and none of 5 dermatofibrosarcoma protuberans.

CONCLUSION

Although PGP9.5 is not a specific marker for MPNST, it is a more sensitive marker than S100 protein (94% vs 38%). When there is a lack of S100 protein expression and a broad panel of immunostains, such as cytokeratin, epithelial membrane antigen, and smooth muscle actin, yields only focal or equivocal staining, PGP9.5 is a useful diagnostic adjunct in confirming the neural origin of a spindle cell sarcoma.

Calretinin and other mesothelioma markers in synovial sarcoma: analysis of antigenic similarities and differences with malignant mesothelioma

Synovial sarcoma (SS) is a mesenchymal neoplasm that typically shows epithelial differentiation. SS commonly metastasizes to lung and pleura, and has also been reported as the primary in these locations. The histologic distinction of SS from mesothelioma may be difficult because of the combination of epithelioid and spindle cells, potentially shared locations, and antigenic expression. In this study the authors examined 103 well-documented SSs including 41 biphasic, 44 monophasic, and 18 poorly differentiated SSs in comparison with 23 epithelioid and seven sarcomatous mesotheliomas. Most biphasic SSs (29 of 41, 71%) had fields or foci of calretinin-positive tumor cells. The spindle cell components were more often positive (55%), whereas 14% of tumors had positive epithelial cells. The monophasic and poorly differentiated SSs commonly had foci of calretinin-positive cells (in 52% and 56% of cases respectively). In comparison, all 23 epithelioid mesotheliomas (EM) were extensively calretinin positive and seven sarcomatoid mesotheliomas were variably calretinin positive. HBME-1 positivity was similarly detected in biphasic SS and EM (100% and 87% respectively). Among the other sarcomas, two of 15 malignant peripheral nerve sheath tumors were focally calretinin positive, whereas 16 epithelioid sarcomas, 20 leiomyosarcomas, 20 gastrointestinal stromal tumors, and 20 angiosarcomas were negative. Biphasic SSs differed from mesotheliomas by their more common BerEp4 positivity (90%) whereas EMs showed focal reactivity in 13% cases. Marked CD15 reactivity was rare in both. Wilms tumor protein-1 (WT1) was not detected in SS, but was present in 12 of 17 EMs. CD141 was rare in SS, limited to spindle cell components, whereas EMs typically showed prominent membrane staining in epithelial cells. Simple epithelial keratins were present in all epithelial cells of biphasic SS and mesothelioma (keratin 7[K7], K19), but were only focal in monophasic and poorly differentiated SS. Biphasic SSs were extensively K14 positive (89% of cases), whereas epithelial and sarcomatoid mesotheliomas typically showed only scattered positive cells. The potentially shared calretinin patterns in SS and mesothelioma require the use of other markers. The discriminating features include extensive BerEp4 positivity, rarity of CD141, and lack of WT1 in SS. Global expression of K7 and K19 in mesotheliomas versus focal expression in monophasic and poorly differentiated SSs, and differential patterns of K14 expression may also be helpful.

Expression of E-cadherin in bone and soft tissue sarcomas: a possible role in epithelial differentiation

The cadherin-mediated cell-cell adhesion system is now known to play a critical role in both the morphogenesis of cancer cells and suppression of their invasion. However, the pattern of expression of E-cadherin, the major cadherin of epithelial cells in bone and soft tissue sarcomas, remains unclear. This prompted us to study E-cadherin expression in a variety of bone and soft tissue sarcomas. Using the monoclonal antibody HECD-1, raised against the extracellular domain of E-cadherin, we observed immunoreactivity in 1 pleomorphic rhabdomyosarcoma, 2 of 5 diffuse mesotheliomas, 4 of 5 clear cell sarcomas, 1 of 5 epithelioid sarcomas, and 10 synovial sarcomas. Other types of bone and soft tissue sarcoma (4 osteosarcomas, 4 chondrosarcomas, 3 primitive neuroectodermal tumors, 1 fibrosarcoma, 4 malignant fibrous histiocytomas, 5 liposarcomas, 4 leiomyosarcomas, 6 alveolar and 5 embryonal rhabdomyosarcomas, 4 angiosarcomas, 4 malignant peripheral nerve sheath tumors, 2 extraskeletal myxoid chondrosarcomas, 2 extraskeletal osteosarcomas, and 3 alveolar soft part sarcomas) were completely negative for E-cadherin. Our findings indicate that E-cadherin is expressed in certain kinds of soft tissue sarcomas, especially those with epithelioid features, suggesting that E-cadherin plays a role in the constitution of their architecture.

Poorly differentiated synovial sarcoma: an analysis of clinical, pathologic, and molecular genetic features

Poorly differentiated synovial sarcoma is a variant of synovial sarcoma in which the tumor cells lack the bland spindle cell appearance of the usual type monophasic synovial sarcoma. Although poorly differentiated synovial sarcoma has been recognized as an entity for many years, no series addressing the clinicopathologic features of this variant have appeared. We describe the histologic, immunohistologic, and molecular findings of a series of 20 poorly differentiated synovial sarcomas. Three types of poorly differentiated synovial sarcoma can be recognized: a large cell epithelioid variant, a small cell variant, and a high-grade spindle cell variant. Epithelial membrane antigen reactivity was seen in 95% of cases, and reactivity for cytokeratin was seen in 42%. The S100 antigen was expressed in 63% of cases. Electron microscopic findings in poorly differentiated synovial sarcoma parallel those found in usual type synovial sarcoma. In 10 cases, material was available for molecular studies; 9 of 10 cases showed the presence of t(X;18) or the associated fusion gene product. These data indicate that poorly differentiated synovial sarcoma is a lesion that shares immunologic, ultrastructural, and molecular characteristics with the usual synovial sarcoma. Follow-up data were available in 16 patients with a mean follow-up of 39 months. Eight patients died with a mean survival time of 33 months. Poorly differentiated synovial sarcoma is a variant of synovial sarcoma that may be associated with a poor prognosis.

Synovial sarcoma

Synovial sarcoma is a rare soft tissue tumor of children and adults that is unrelated to synovium and can occur in almost any part of the body. The familiar biphasic synovial sarcoma has discernible glandular or solid epithelial structures, and monophasic forms have characteristic ovoid or spindle cells with only immunohistochemical or ultrastructural evidence of epithelial differentiation. There are several morphologic patterns, including myxoid and hemangiopericytic, and behaviorally distinct calcifying, ossifying, and poorly differentiated subtypes can be recognized. Most synovial sarcomas are immunoreactive for cytokeratin, epithelial membrane antigen, and bc12 protein, and negative for CD34, and many express S100 protein and CD99 (MIC2). Nearly all synovial sarcomas have a specific t(x;18) (p11.2;q11.2) chromosomal abnormality, resulting in fusion of either of two variants of the SSX gene with the SYT gene; the genetic features may relate to morphology and outcome. The differential diagnosis can include a wide range of spindled, polygonal, or round cell sarcomas. Clinically, there have been marked recent improvements in local control of disease and lesser ones in management of metastases. The pathology, differential diagnosis, and behavior of this unique tumor are reviewed.

A case of a malignant mixed tumor in the vagina

Malignant mixed tumors in the vagina are extremely rare. We experienced a case of a malignant mixed tumor (synovioid variant). Surgical treatment was performed, followed by 3 courses of chemotherapy. Up to the present time, 4 years after the first treatment, no signs of recurrence have been observed.

The Role of Immunohistochemistry in the Differential Diagnosis of Soft-Tissue Tumors

This regular feature presents special issues in oncologic pathology.

Detection of chromosome 18 rearrangement in synovial sarcoma by fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH) evaluations of chromosome 18 were performed in synovial sarcoma, hemangiopericytoma, and mesothelioma. Each case was evaluated with centromeric and whole chromosome paint probes. The synovial sarcomas had t(X;18) cytogenetically, but the FISH evaluator was blinded to the cytogenetic results and to the histopathologic diagnosis. The FISH analyses were consistent with chromosome 18 translocation in 6 of 7 synovial sarcomas, 0 of 3 hemangiopericytomas, and 0 of 1 mesothelioma. These findings support the use of FISH in the diagnosis of synovial sarcoma.

Biphasic synovial sarcoma in the small intestinal mesentery

BACKGROUND

A 46-year-old man presented with recurrent anemia and polyarthralgia. Investigations revealed a mass in the ileal mesentery, which was resected. Results of routine histologic examination suggested a diagnosis of synovial sarcoma, a rare malignancy usually not reported at this site.

METHODS

Tissue was examined immunohistochemically, ultrastructurally, and by fluorescent in situ hybridization to confirm the diagnosis.

RESULTS

Immunohistochemical studies revealed widespread labeling for cytokeratins and focal labeling for desmin and vimentin in the epithelial component, with labeling for epithelial membrane antigen in the epithelial and spindle-cell components. Fluorescent in situ hybridization analysis showed the characteristic t(X;18) translocation of synovial sarcoma.

CONCLUSIONS

This is a unique case of synovial sarcoma in the small intestinal mesentery. Immunohistochemical labeling confirmed the diagnosis, although, to the authors' knowledge, the pattern of desmin labeling has not been described previously. The clinical association with polyarthralgia, which resolved after removal of the neoplasm, also has not been described previously.

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.

Interphase cytogenetic analysis of distinct X-chromosomal translocation breakpoints in synovial sarcoma

Synovial sarcomas show a specific translocation involving chromosomes X and 18, t(X;18)(p11.2;q11.2). Two distinct X-chromosomal breakpoints occur in different synovial sarcoma tumour samples. These breakpoints are located within two related genomic regions containing ornithine aminotransferase-like sequences, termed OATL1 and OATL2. Preliminary observations indicated the potential correlation of OATL1-associated breakpoints with biphasic tumours and OATL2-associated breakpoints with monophasic fibrous tumours. The present study uses interphase cytogenetics to investigate the nature of chromosomal aberrations in frozen synovial sarcoma tissue samples. Two-colour fluorescence in situ hybridization (FISH) was performed using probes specific for the centromeres of chromosome X or 18, along with yeast artificial chromosome probes corresponding to the distinct breakpoint regions on Xp. One monophasic epithelial and two monophasic fibrous synovial sarcomas showed an OATL2-associated breakpoint, while a biphasic tumour revealed a hybridization pattern indicating a breakpoint within the OATL1 region. These results confirm our previous suggestion of a relationship between alternative breakpoints in Xp11.2 and different histological phenotypes observed in synovial sarcomas. They also demonstrate the utility of the two-colour hybridization approach for the identification of chromosomal changes in interphase nuclei isolated from frozen tissues.

Immunohistochemical analysis of extracellular matrix components in synovial sarcoma

Little attention has been paid to the composition of the extracellular matrix in synovial sarcoma, a tumour showing both epithelial and mesenchymal phenotypes. As extracellular matrix participates actively in interactions between epithelial and mesenchymal tissues, further knowledge of the pathogenesis of this tumour may be provided by the study of extracellular matrix components. Therefore, we have analysed the immunohistochemical distribution of type I, III, and IV collagen, fibronectin, laminin and tenascin in four cases of synovial sarcoma. The pattern of immunoreactivity for these molecules varied according to the tissue phenotype of the tumour. Mesenchymal tissue labelled mainly for type I and III interstitial collagen and fibronectin. The epithelial component was surrounded by a laminin and type IV collagen-positive basement membrane, but punctate pericellular reactivity for laminin and type IV collagen was also detected among some mesenchymal cells. Tenascin was strongly expressed in the mesenchymal tissue immediately around epithelial structures and weakly or not at all expressed in the monophasic tumours and in mesenchymal tissue distant from epithelial elements in the biphasic tumours. These results suggest some resemblances between synovial sarcoma and the embryonic development of epithelia from mesenchymal cells, providing further support for the concept of an epitheliogenesis from the mesenchyme in these tumours.

Immunohistochemical profile of synovial sarcoma with emphasis on the epithelial-type differentiation. A study of 49 primary tumours, recurrences and metastases

The relationship between biphasic (BSS) and monophasic (MSS) subtypes of synovial sarcoma (SS) as well as the relationship between cells of solid/glandular areas and the spindle cells of BSS remain controversial. In order to further evaluate the immunohistochemical phenotype of SS we studied 34 primary tumours (15 BSS; 19 MSS), 7 recurrences (4 from primary BSS; 3 from primary MSS) and 8 metastases (7 BSS; one MSS), using several antibodies (EMA, CEA, keratins 1, 4, 5/6, 7, 8, 13, 18, 19, 20, vimentin, collagen IV and laminin) that work in paraffin-embedded material. Spindle cells outside solid/glandular areas of BSS and in MSS showed immunoreactivity for keratins 5/6, 7, 8, 18 and 19. The transition of solid/glandular areas to surrounding spindle cells also showed keratin staining and failed to show a distinct separation regarding the immunoreactivity for laminin and collagen IV. Peripheral cells of solid/glandular areas were immunoreactive for vimentin. No major differences were observed between immunophenotypical cell profiles of BSS and MSS, apart from the exclusive immunostaining of solid/glandular areas of BSS for keratin 13 and CEA. Downgrading of keratin and extracellular matrix antigens immunoreactivity was observed when primary tumours were compared to recurrent and/or metastatic tumours of both subtypes (MSS and BSS). We conclude that SS should be regarded as carcinomas of soft tissues with an immunohistochemical phenotype depending on the degree of epithelial differentiation: spindle cells (MSS and BSS) predominantly expressing simple keratins, and poorly differentiated (solid/glandular) as well as well-differentiated (glandular) areas (BSS) expressing, in addition, complex epithelial-type keratins.

Case report 805: Synovial sarcoma, epithelial hyperplasia in the humeral air sacs, and formation of medullary bone

In summary, we have reported a most interesting case of synovial sarcoma, epithelial hyperplasia in the air sacs, and formation of medullary bone in the left humerus of a 5-year-old female white pigeon. The tumor showed aggressive features radiologically and caused dysfunction of the left wing. The histologic findings and immunohistochemical reactions in this report were identical in many respects to the manifestation of synovial sarcoma described in human beings and dogs. Formation of medullary bone in female birds during the reproductive phase and hyperplasia of epithelia in the air sacs were also discussed.

Identification of a yeast artificial chromosome (YAC) spanning the synovial sarcoma-specific t(X;18)(p11.2;q11.2) breakpoint

A somatic cell hybrid containing the synovial sarcoma-associated t(X;18)(p11.2;q11.2) derivative (der(X)) chromosome was used to characterize the translocation breakpoint region on the X chromosome. By using Southern hybridization of DNA from this der(X) hybrid in conjunction with Xp-region specific radiation reduced cell hybrids and probes, it was found that this breakpoint maps within the ornithine aminotransferase (OAT) L1 cluster. A yeast artificial chromosome (YAC) clone (OAT YAC2) which hybridizes to a human OAT cDNA probe and is known to contain part of the OATL1 cluster was selected and used to confirm these results both by fluorescence in situ hybridization on synovial sarcoma patient material and by hybridization of its end-clones to the der(X) containing hybrid cells. It was found that indeed the human Xp sequences contained within this YAC are split as a consequence of the (X;18) translocation. Therefore, we conclude that OAT YAC2 spans the synovial sarcoma-specific translocation breakpoint and, as such, may serve as an ideal starting point from which the gene(s) involved in the development of this soft tissue tumor can be isolated.

Synovial sarcoma. Inter-relationship of the biphasic and monophasic subtypes

In order to assess minimum diagnostic criteria for synovial sarcoma, particularly the monophasic variety, and the inter-relationship between the monophasic and biphasic types, 32 examples were studied histologically, immunohistochemically (26 cases), and ultrastructurally (13 cases). Of the six biphasic synovial sarcomas examined by electron microscopy, the spindle cell component did not show evidence of epithelial differentiation or resemble the epithelial phase, but did appear fibroblastic; no tumor cells transitional between the spindle and epithelial component were evident. In contrast, all of the seven monophasic lesions had ultrastructural growth patterns and some cellular features approximating the epithelial cells of the biphasic variant. In 11 biphasic synovial sarcomas, epithelial membrane antigen was detected in the glandular epithelium of all cases and cytokeratins in eight cases; in no case were these antigens detected in the spindle cell regions of biphasic lesions. Of the 15 monophasic synovial sarcomas, two were positive for cytokeratins and four for epithelial membrane antigen. Thus, the detection of epithelial markers either immunohistochemically or by electron microscopy (or both) should be the minimal diagnostic criteria for monophasic synovial sarcomas. Based on these findings, it is suggested that monophasic synovial sarcomas do not represent the spindle cell or "stromal" phase of biphasic synovial sarcomas, but are a poorly differentiated variant of the latter. As others have suggested, these tumors are, in fact, carcinosarcomas and carcinomas of the soft tissues and the designation synovial sarcoma is inappropriate for this tumor class.

Usefulness of antikeratin immunoreactivity in osteosarcomas of the jaw

The immunohistochemical typing of cytoplasmic intermediate filaments has proved helpful to the pathologist in classifying poorly differentiated malignant neoplasms. In general, identification of keratin-type intermediate filaments has been associated with epithelial histodifferentiation, but several exceptions to this generalization have been reported in the literature. A recent report identified false-positive immunostaining for keratin in osteosarcomas of the jaws that was attributed to cross-reactivity induced by enzyme digestion of the tissue specimens before immunostaining. Because the jaws are unique in the skeletal system because of their relatively high incidence of intraosseous epithelial neoplasms, false-positive immunoreactions for keratin could complicate differentiating sarcomatoid epithelial neoplasms from poorly differentiated osteosarcomas. To evaluate this possible pitfall in our laboratory, eight osteosarcomas of the jaws were evaluated for keratin immunostaining with polyclonal and monoclonal antibodies on tissue sections that had been enzymatically treated with protease. No immunostaining was demonstrated in these tumors. Repudiation of the usefulness of antikeratin immunohistochemistry for intraosseous jaw tumors was not confirmed with the procedures used in our laboratory.

Rhabdoid tumors of soft tissues: a clinicopathologic study of 26 cases enrolled on the Intergroup Rhabdomyosarcoma Study

Twenty-six cases of malignant soft tissue tumors with features similar to renal rhabdoid tumors were identified among approximately 3,000 childhood sarcomas entered on Intergroup Rhabdomyosarcoma Studies I-III. The tumors consisted of polygonal cells with vesicular nuclei and prominent nucleoli and cytoplasmic intermediate filament inclusions as identified by electron microscopy and immunohistochemistry. The growth pattern was predominantly solid or solid-trabecular. Immunohistochemistry showed vimentin, wide spectrum keratin, and epithelial membrane antigen to be the most consistent antigenic phenotypes. Eleven patients were infants less than 1 year of age. The tumors affected predominantly soft tissues of proximal extremities, trunk, and retroperitoneum/pelvis/abdomen. Nineteen patients died within 1 to 82 months (median, 6 months) from the start of treatment. Five patients have survived the disease for 2 to 13 years. When compared with the survival analysis of 991 Intergroup Rhabdomyosarcoma Study II patients, it was obvious that this group of tumors fares very poorly (P less than .001). The tumor belongs to the group of soft tissue neoplasms showing mesenchymal and subtle epithelial differentiation, similar to epithelioid sarcoma. Because of its identifiable histology, site and age distribution, and poor outcome, it warrants a status as an independent entity.

Synovial sarcoma: a review and update, with emphasis on the ultrastructural characterization of the nonglandular component

Classic biphasic synovial sarcoma is usually not a problem in identification, whereas the monophasic spindle cell form continues to be a challenge in the differential diagnosis of spindle cell neoplasms. Most synovial sarcomas do not arise from a joint or tendon sheath, and by electron microscopy and immunohistochemistry they differ in several ways from nonneoplastic synovium. The cell of origin of synovial sarcoma is unknown, but certain features are rather consistently observed in the biphasic tumors and are useful in identifying monophasic samples. These features are apparent by immunohistochemistry and electron microscopy, both of which indicate early epithelial differentiation in the nonglandular component of the neoplasm. With immunohistochemistry, some of these cells stain for keratin. By electron microscopy, a gradient of differentiation from unclassifiable spindle cells to fully differentiated epithelial lining cells is demonstrable. A review and illustration of the ultrastructural characteristics in this spectrum of intermediate cells constitute the main emphasis of the article. The cells tend to be oval and polygonal; to be arranged in clusters surrounded by basal lamina or flocculent matrix; to have junctions, including tight junctions, and to form villuslike filopodia, true microvilli, canaliculi, and microlumina. This range of ultrastructural features is usually diagnostic of the nonglandular phase of synovial sarcoma.

Synovial sarcoma: a clinicopathological study of 36 cases

Thirty-six cases of synovial sarcoma (13 biphasic and 23 monophasic) were subjected to a clinicopathologic study that included electron microscopy and immunohistochemistry. The group consisted of 21 males and 15 females ranging in age from 2 to 63 years. The majority of tumors (27 cases) were found in the hip and lower extremity. Immunohistochemical study revealed that keratin, which was detected in 92% of the biphasic and 57% of the monophasic tumors, was a more sensitive marker of epithelial differentiation than EMA or CEA. The overall 5-year survival of the patients was 64%. Male sex, older age, presence of tumor necrosis, monophasic pattern, and absence of keratin positivity had an unfavourable effect on survival but lacked statistical significance. Survival was significantly lower in patients with tumors exhibiting more than 15 mitoses per 10 HPF (P less than .02) and in those with tumors showing necrosis and a mitotic rate greater than 5 mitoses per 10 HPF (P less than .005).

Cytokeratin expression in malignant Triton tumor

A malignant Triton tumor in a 9-year-old boy is described. The first biopsy which was taken from the thenar prominence was diagnosed as a monophasic fibrous synovial sarcoma based on the finding of a spindle cell neoplasm with plump nuclei and cytokeratin expression. The true nature of the tumor became apparent when a second biopsy was investigated. In this specimen a rhabdomyosarcomatous component was found in association with a spindle cell sarcoma fulfilling the criteria of a malignant schwannoma. Immunohistochemical staining using antibodies against vimentin, desmin, muscle-specific actin, cytokeratin, glial fibrillary acidic protein, protein S-100, Leu 7 and myoglobin served to distinguish the two tumor components and documented the possible reactivity of malignant Triton tumor for cytokeratins.

Synovial sarcoma: an immunohistochemical and ultrastructural study

Thirty-nine primary synovial sarcomas (15 biphasic, 24 monophasic), and 19 metastatic synovial sarcomas were studied with a battery of antibodies directed to keratin, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), vimentin, desmin, muscle-specific actin, smooth muscle actin, S-100 protein, Leu-7, chromogranin A, laminin, collagen IV, Ulex europaeus agglutinin I (UEAI), and the HMB-45 antimelanoma antibody. Twenty-two primary and 18 metastatic synovial sarcomas were also examined by electron microscopy. Epithelial and/or spindle cells in every biphasic tumor, primary and metastatic, reacted for keratin and EMA, but only six primary tumors (five biphasic and one monophasic) showed weak reactivity for CEA which, in the biphasic tumors, was confined to the epithelial component. Of the monophasic tumors, 15 primary (63%) and four metastatic (25%) stained for keratin, whereas seven primary (29%) and two metastatic (13%) tumors reacted for EMA. Only one primary monophasic synovial sarcoma stained for CEA. Tumors that stained for EMA or CEA also stained for keratin which is, therefore, the most useful epithelial marker. Immunostaining for epithelial markers, UEAI, collagen IV, and laminin serves to delineate the epithelial component when it is obscure in routine sections. Electron microscopy facilitates the diagnosis when epithelial markers are not expressed and aids in separating monophasic synovial sarcomas from other sarcomas that they resemble by light microscopy.

The value of electronmicroscopy and immunohistochemistry in the diagnosis of soft tissue sarcomas: a study of 200 cases

Two hundred soft tissue sarcomas, accrued consecutively over a 4-year period, were examined by light and electronmicroscopy and by routine immunohistochemistry. The commonest tumour type was malignant fibrous histiocytoma. Fibrosarcoma, composed only of fibroblasts, was diagnosed in only one case; three others, composed also of myofibroblasts, could be regarded as fibrosarcomas or myofibrosarcomas. Immunohistochemistry was of most value in the diagnosis of rhabdomyosarcoma, leiomyosarcoma, malignant peripheral nerve sheath tumour of Schwann cell type and epithelioid sarcoma. Electronmicroscopy was of most use for the diagnosis of malignant peripheral nerve sheath tumour of perineurial cell type and marker-negative monophasic synovial sarcoma, and for confirming malignant fibrous histiocytoma. Fifteen of 19 marker-negative spindle cell tumours (79%) were diagnosable by electronmicroscopy. A combination of techniques resulted in a specific diagnosis in 193 cases (96.5%). The routine use of electronmicroscopy in sarcoma diagnosis can improve accuracy of diagnosis, establish the true frequency of marker-positivity for each ultrastructurally confirmed tumour type and minimise the number of unclassifiable cases.

Epithelial differentiation in synovial sarcoma. Correlation with histology and immunophenotypic expression

The epithelial properties of the cells in six cases of synovial sarcoma, five biphasic and one monophasic, were examined. Epithelial cells formed well demarcated glandular nests with a multi- or single-layered lining, poorly defined nest-like clusters, or appeared as scattered single plump cells in a spindle-cell stroma. Keratinization was seen in multi-layered epithelia, and was suggested in single-layered epithelia from the presence of some enlarged eosinophilic cells. Immunohistochemically, epithelia lining glands showed reactivity for both low- and high-molecular-weight (MW) cytokeratins, and the reactions for both were strongest in keratinized cells. Clustered or single plump cells showed low-MW cytokeratin reactivity. All epithelial cells were negative for the largest cytokeratin (no. 1), and occasionally stained positively for vimentin. Spindle-shaped stromal cells usually stained positively for vimentin only. Type IV collagen was distributed linearly around well circumscribed epithelia, but not around poorly defined epithelia or plump cells. Epithelial membrane antigen was distributed linearly along glandular spaces and irregularly or granularly in clustered plump cells. The immunophenotypic epithelialization in synovial sarcoma was restricted, but showed considerable correlation with the histological grade of differentiation.

Cytogenetic findings in two synovial sarcomas

Cytogenetic analysis was performed after short-term tissue culture of two recurrent synovial sarcomas. The tumors were classified on the basis of morphology, location, and immunohistochemistry. In a poorly differentiated tumor, the karyotype 49,XY, +7, +8, +19,t(5:18) (q11.2;q11.2), and in a biphasic tumor two clonal cell lines with common translocations t(X;18)(p11.2;q11.2) and t(12;17)(p11.2;q11.2) were present. In the predominant cell line several other structural aberrations including t(1;12)(q21;q24.3), t(3;18)(p23;q21), and 17p+ were found. A comparison of our results with previously published studies suggests that in addition to t(X;18), translocations of chromosome 18 with other chromosomes may represent a consistent feature of chromosomal changes in synovial sarcoma.

A case of synovial sarcoma with abnormal expression of the human retinoblastoma susceptibility gene

Abnormal or absent expression of the human retinoblastoma susceptibility (RB) gene has been implicated in the genesis of retinoblastoma. In addition to a 90% chance of developing retinoblastoma, patients inheriting a mutant RB gene have a high incidence of second nonocular malignancies, suggesting a role for this gene in other tumors as well. This report describes a patient without a previous history of retinoblastoma who developed metastatic synovial sarcoma. Analysis of RNA from this tumor revealed the presence of an abnormally long RB gene transcript in addition to an RB transcript of normal length. On the basis of findings in retinoblastoma, we propose that alteration of RB gene expression was significantly related to the formation of this patient's synovial sarcoma.

Keratin protein immunoreactivity of sarcomatoid and mixed types of diffuse malignant mesothelioma: an immunoperoxidase study of 30 cases

To define the role of keratin protein immunohistochemistry in the pathologic diagnosis of the sarcomatoid type of diffuse malignant mesothelioma (DMM), we examined 30 DMM (16 pure sarcomatoid type and 14 mixed sarcomatoid-epithelial type) by an indirect immunoperoxidase technique using three commercially available antibodies to keratin proteins. The sarcomatoid (spindle-cell) areas of all 30 cases of sarcomatoid DMM were immunoreactive for keratin proteins. In 14 of 16 cases of sarcomatoid DMM, 50% or more of the tumor cells were reactive with one or more antibodies; however, polyclonal bovine muzzle and monoclonal AE1/AE3 antibodies were distinctly superior to polyclonal human callus keratin antibody in the detection of spindle tumor cells. In contrast with the staining patterns observed for DMM, 39 spindle-cell malignancies and tumor-like processes of 10 histogenetic types were unreactive with the three antibodies. Those spindle-cell tumors and reactive mesothelial proliferations that may enter into the differential diagnosis of sarcomatoid DMM are discussed. We conclude that keratin protein immunohistochemistry is a sensitive and highly useful method for the pathologic diagnosis of the sarcomatoid type of DMM and its distinction from other spindle-cell neoplasms.

Synovial sarcoma of the heart arising from a so-called mesothelioma of the atrio-ventricular node

A primary tumour of the right atrium with morphological, ultrastructural and immunohistochemical features of a synovial sarcoma is described. This appeared to have arisen from a benign so-called mesothelioma of the atrio-ventricular node and had metastasized to the lungs. The histogenesis and relationship of these two tumours are discussed.

Cytokeratins in certain endothelial and smooth muscle cells of two taxonomically distant vertebrate species, Xenopus laevis and man

Using immunolocalization techniques, electron microscopy, and gel electrophoresis combined with immunoblotting, we have noted remarkable interspecies differences in the expression of cytokeratins in certain nonepithelial cells. In the present study we describe, in two taxonomically distant vertebrate species, the African clawed toad Xenopus laevis and man, endothelial and smooth muscle cells which express cytokeratin intermediate filaments (IFs), in addition to vimentin and/or desmin IFs. In Xenopus, all endothelia seem to produce both vimentin and cytokeratin IFs. As well, certain smooth muscle bundles located in the periphery of the walls of the esophagus and the urinary bladder produce small amounts of cytokeratin IFs in addition to IFs containing vimentin or desmin or both. The amphibian equivalents of human cytokeratins 8 and 18 have been identified in these nonepithelial tissues. In human endothelial cells, immunocytochemical reactions with certain cytokeratin antibodies are restricted to a rare subset of blood vessels. Vessels of this type were first noted in synovial and submucosal tissues, but also occur in some other locations. Cytokeratins have also been detected in certain groups of smooth muscles, such as those present in the walls of some blood vessels in synovial tissue and umbilical cord. Here, the synthesis of low levels of cytokeratins 8 and 18, sometimes with traces of cytokeratin 19, has been demonstrated in smooth muscle cells by colocalization with myogenic marker proteins, such as desmin and/or the smooth-muscle-specific isoform of alpha-actin. Possible reasons for the differences in cytokeratin expression between adjacent endothelia in man, and smooth-muscle structures in both species, as well as biologic and histodiagnostic implications of these findings, are discussed.