Authors: Paul H Hartel, John E. Parker.
Primary pleuro-pulmonary synovial sarcoma is rare and poses a diagnostic challenge particularly when poorly differentiated. We present 15 cases of poorly differentiated primary pleuro-pulmonary synovial sarcoma and compare and contrast results with previously published series on usual better differentiated tumors. Clinical and radiologic findings were similar to usual pulmonary synovial sarcoma with typical imaging features. 7 of 10 patients with outcome data died of disease within 5 years. Histologically, tumors had densely cellular fascicles, hyalinized stroma, hemangiopericytoma-like vasculature, and focal myxoid change. Round cell and rare rhabdoid morphology were unique to poorly differentiated tumors. Immunohistochemistry demonstrated at least focal expression of pancytokeratin, EMA, CK7, CK5/6, calretinin, and CD56, and diffuse positivity with CD99 and bcl-2. Ten primary pulmonary synovial sarcomas with tissue available for study were positive for t(x;18), with a more even distribution of SS18/SSX1 and SS18/SSX2 tumors compared with better differentiated lung synovial sarcomas. In conclusion, our study confirms that clinical, histological, and immunohistochemical data from poorly differentiated primary pleuro-pulmonary synovial sarcoma is similar to better differentiated tumours but special caveats remain for accurate histopathologic diagnosis.
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