Molecularly confirmed primary prostatic synovial sarcoma.

We report the second molecularly-confirmed primary prostatic synovial sarcoma. The diagnosis was particularly elusive at the light microscopic level in that the tumor failed to show epithelial differentiation, but it did show combined spindle-cell and poorly differentiated (round-cell) morphologies. The immunohistochemical staining profile was nonspecific and potentially misleading. Only by demonstration of the characteristic SYT-SSX gene fusion of synovial sarcoma by reverse transcriptase polymerase chain reaction (RT-PCR) analysis of RNA extracted from archival material could the diagnosis be confirmed. This case further illustrates the use of this technique in diagnostic pathology.