Primary monophasic synovial sarcoma of the pleura - Five cases confirmed by the presence of SYT-SSX fusion transcript

This study reports five cases of primary pleural monophasic synovial sarcom as and assesses the role of the SYT-SSX fusion transcript in the differenti al diagnosis. Patients had a mean age of 47 years with no gender predilecti on. Chest pain and pleural-based masses with effusions characterized the cl inical presentations. Each patient underwent a complete surgical resection of the mass. The mean follow-up was 9 months, available in four patients. T hey were all alive, with no evidence of disease. Histologically, neoplasms were composed of densely packed fusiform cells focally alternating with les s cellular areas. No epithelial differentiation was identified at the hemat oxylin and eosin level. Keratin and epithelial membrane antigen reactivity was focal and present in four and two tumors, respectively. There was no im munoreactivity for CD34. RT-PCR studies for the presence of a SYT-SSX1 or S YT-SSX2 fusion transcript were positive in every tumor. In comparison, 10 l ocalized fibrous tumors were immunohistochemically negative for keratin and epithelial membrane antigen and positive for CD34. A SYT-SSX fusion transc ript was not identified in any of five localized fibrous tumors tested. Ide ntification of the synovial sarcoma-specific chimeric transcript (SYT-SSX1 or SYT-SSX2), in conjunction with immunoperoxidase studies, can be extremel y helpful in identifying cases of pleural monophasic synovial sarcoma.