Synovial sarcoma of the abdominal wall. Light microscopic, histochemical and electron microscopic investigations

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.

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.

Demonstration of myxoid change in fine-needle aspiration of synovial sarcoma: a case report

We report a case of synovial sarcoma with extensive myxoid change diagnosed by fine-needle aspiration. The patient is a 46-year-old woman who presented with a right paratibial mass. Aspiration cytology demonstrated a spindle cell neoplasm consistent with a synovial sarcoma but containing a prominent myxoid matrix. The clinical suspicion and cytologic diagnosis of a synovial sarcoma was confirmed by histologic and immunohistochemical findings. The cytologic differential diagnosis of spindle cell neoplasms with extensive myxoid change should be broadened to include synovial sarcoma.

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.

Synovial sarcoma of the abdominal wall

BACKGROUND

Synovial sarcoma usually arises in the extremities and in close proximity to large joints. Reported examples arising in the anterior abdominal wall are rare. Because most accounts from this location consist of case reports, neither clinical nor prognostic features have been well delineated.

METHODS

Twenty-seven synovial sarcomas of the abdominal wall (SSAW), retrieved from the Soft Tissue Registry of the Armed Forces Institute of Pathology, were reviewed and analyzed retrospectively. Immunohistochemical stains were performed in 18 cases.

RESULTS

There were specimens from 12 male and 15 female patients, ranging in age from 8 to 58 years (median, 23 years). The tumors were classified as biphasic (14), predominantly monophasic fibrous (8), and poorly differentiated (5) types. The neoplasms occasionally were cystic and typically reacted, at least focally, with antibodies directed against keratin and/or epithelial membrane antigen. Eight tumors were smaller than 5 cm.; 17 tumors were 5 cm or larger in size. Dimensions were not recorded in two cases. Follow-up, ranging from 1 to 264 months, was obtained in 18 cases. Nine individuals were alive and well and eight were dead of disease at median follow-up intervals of 98 and 26 months, respectively. One patient was dead with disease, possibly secondary to chemotherapy-related causes. All nine patients who have died had clinical evidence of metastatic disease. Patients who presented with tumors 5 cm or larger had a less favorable outcome than whose with tumors smaller than 5 cm. (58% versus 40% mortality). A positive correlation was noted between increased mitotic activity and the mortality rate. Although patients with biphasic and predominantly monophasic fibrous tumors had a similar mortality rate (40% for both groups), patients with poorly differentiated synovial sarcoma fared worse (100% mortality). In general, poorly differentiated synovial sarcomas had a higher mitotic rate than either biphasic or monophasic fibrous examples. No appreciable difference in survival was evident based on the age at presentation (< 15 versus > or = 15 years of age).

CONCLUSIONS

The survival rate for patients with SSAW is similar to that reported for synovial sarcoma in general. A high mitotic rate and the poorly differentiated subtype of synovial sarcoma both were associated with a poor prognosis and, to some extent, appear interrelated. Less favorable behavior also was noted when the tumors were large (> or = 5 cm). Pluripotential or arthrogenous mesenchyme may be implicated in the pathogenesis of these tumors.

Synovial sarcoma. A clinicopathological study of 31 cases

Thirty-one surgically treated cases of synovial sarcoma were reviewed. The mean age of the patients at primary surgery was 37 years (range 10-78 years). Twenty-nine of the tumors were of the biphasic type and two were monophasic. Currently a monophasic synovial sarcoma can be considered as a specific entity. In contrast to other soft-tissue sarcomas, synovial sarcomas present the characteristics of a carcinosarcoma. The 5-year survival rate in this study was 55% and the 6-year survival rate 50%; after 6 years there were no recurrences. The primary treatment should follow the same guidelines that are currently given for other soft-tissue sarcomas: wide and radical excisional margins should be aimed at. Excisional treatment even of repeated pulmonary recurrences may be rewarding.

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: ultrastructural and immunohistochemical features of epithelial differentiation in monophasic and biphasic tumors

Nineteen synovial sarcomas, six biphasic and 13 monophasic tumors, were examined by light and electron microscopy and immunohistochemically for the presence of the epithelial markers keratin and epithelial membrane antigen (EMA). Ultrastructurally, intercellular spaces with processes are present to varying degrees in the spindle cell component of all synovial sarcomas, and junctional specializations occur in most cases. Tumors of the two types differ in their content of external (basal) lamina, which encloses the epithelial component of all biphasic tumors and is detectable in the spindle cell component of two thirds of them, but is absent from the majority of monophasic tumors. Keratin and EMA were demonstrated in both components of all six biphasic tumors. Of the 13 monophasic tumors, keratin was present in nine, EMA in eight, and at least one epithelial marker in ten. Synovial sarcoma is regarded as a distinctive soft tissue tumor with variable epithelial-like differentiation. The use of electron microscopy can increase the specificity of immunohistochemical studies of soft tissue sarcomas and allow more accurate differentiation of monophasic synovial sarcoma from other spindle cell tumors, particularly those that do not express markers.

Synovial sarcoma with squamous metaplasia

We report on a biphasic synovial sarcoma showing slight squamous cell differentiation of their epithelioid component under the light microscope. The electron microscopical examination revealed numerous tonofilaments arranged in dense bundles, which could be characterized as tonofibrils with keratohyalin granules in the same cells. The presence of such structures indicates the possibility of squamous metaplasia in biphasic synovial sarcoma.

Monophasic synovial sarcoma of spindle-cell type. Epithelial differentiation as revealed by ultrastructural features, content of prekeratin and binding of peanut agglutinin

Monophasic synovial sarcomas of spindle-cell type and fibrosarcomas were studied by electron and immunofluorescence microscopy for their intermediate filament expression and the binding of peanut agglutinin (PNA). In monophasic synovial sarcomas of spindle-cell type (two cases), frequent cell-to-cell junctions, irregular cytoplasmic processes, and occasional cytoplasmic, tonofilament-like bundles of intermediate filaments were seen by electron microscopy. These features were absent from fibrosarcomas. Immunohistologically, the monophasic synovial sarcomas showed arrays of prekeratin-positive cells in the midst of the vimentin-positive spindle cells. By double fluorescence microscopy, the prekeratin-positive cells also bound PNA, like the epithelial-like cells of the classical biphasic synovial sarcoma. In contrast to monophasic synovial sarcomas, prekeratin-positive cells and arrays of PNA-binding cells, were not seen by immunofluorescence microscopy in fibrosarcomas (seven cases). Thus the prekeratin-content, the binding of PNA lectin, and certain ultrastructural features suggesting early epithelial differentiation, help to distinguish monophasic synovial sarcomas of spindle-cell type from other spindle cell sarcomas.

Monophasic synovial sarcoma, epithelioid sarcoma and chordoid sarcoma: ultrastructural evidence for a common histogenesis, despite light microscopic diversity

Ultrastructural examination of six rare sarcomas--four monophasic spindle cell tumours, one epithelioid sarcoma, one chordoid sarcoma--has revealed marked similarities at the electron microscopic level despite widely divergent light microscopic appearances. These features consisted of: 1 the presence of two cell types, viz. a clear cell and a cell resembling the fibroblast; 2 pseudoglandular spaces with projecting microvilli or filopodia, and with related tight junctions; 3 an amorphous intercellular ground substance with focal condensation into recognizable basement membrane. The findings suggest a common maturation of these diverse tumours to synovial-like tissue, and support the proposal of Hajdu Shiu & Fortner (1977) that these be considered variants of synovial sarcoma. Published ultrastructural studies of synovial, epithelioid and chordoid sarcoma are reviewed in the light of these findings. The ultrastructural differentiation of synovial sarcoma from extraskeletal myxoid chondrosarcoma, chordoma and the spectrum of malignant spindle cell tumours is discussed.

Histologic distinction between malignant mesothelioma, benign pleural lesion and carcinoma metastasis. Evaluation of the application of morphometry combined with histochemistry and immunostaining

Thirty men and 7 women with malignant mesothelioma seen at the Free University Hospital from 1st January 1960 until 1st July 1981 were reviewed. The histological, histochemical and morphometrical findings are reported. These findings are compared with 25 cases of pleural metastatic carcinoma and 25 cases of reactive pleural lesions. Fourty-nine percent of malignant mesotheliomas produced hyaluronic acid, however all cases of pleural metastatic carcinomas failed to produce this substance. All cases of malignant mesothelioma were D-PAS negative while 15 cases of pleural metastatic carcinoma showed reactivity to D-PAS. All cases of malignant mesothelioma and 9 cases of metastases were CEA negative. To distinguish malignant mesothelioma from metastases it is advisable to perform the D-PAS staining first. If it is negative mesothelioma can be confirmed by showing hyaluronic acid activity. A positive CEA staining rules out mesothelioma. In our study it was shown that with these methods 18 of 37 mesotheliomas could be identified with certainty, and 22 of the 25 carcinoma metastases. Morphometrically the malignant mesotheliomas could not be distinguished from the metastases, however the reactive pleural lesions had smaller nuclei than the malignant cells with mean values below 30 mu2. In the malignant cases these values had a range from 36 to 101 mu2. In distinguishing between reactive pleural lesions and malignant mesothelioma the production of hyaluronic acid points to the malignant character of the lesion. Thus histochemistry and immunostaining are important in the distinction of malignant mesothelioma from metastases, while the value of morphometry lies mainly in the seperation of reactive lesions from malignant mesothelioma.

Synovial sarcoma enzyme histochemistry of a typical case

A typical case of biphasic synovial sarcoma was studied using enzyme histochemistry. A marked difference between the staining characteristics of the spindle cells and the epithelial-like cells was demonstrated by reactions for various hydrolytic enzymes. The epithelial-like cells exhibited a strong reactivity for alkaline phosphatase, acid phosphatase, adenosine triphosphatase and nonspecific esterase, whereas spindle-cells were completely unreactive when tested for these enzymes. This is, to our knowledge, the first report demonstrating differences in the enzymatic pattern of the two cell populations which compose synovial sarcoma.