Synovial sarcoma arising in the vulva cytogenetically confirmed by SYT break-apart rearrangement fluorescence in situ hybridization: A case report and discussion of diagnostic methods.

Synovial sarcoma (SS) is a soft tissue sarcoma of unknown histogenesis that rarely occurs in the female genital tract. We report a case of SS occurring in the right vulva of a young Japanese female. The tumor was composed of poorly differentiated rounded cell areas, surrounded by fibroblastic spindle-shaped cell areas. Immunohistochemically, the tumor cells were focally positive for cytokeratin, vimentin, CD99, Bcl-2 and neuron-specific enolase. The tumor was suspected, but was difficult to confirm as it was an SS based solely on light-microscopic and immunohistochemical findings. Although reverse transcription polymerase chain reaction (RT-PCR) failed to detect SS-specific SYT-SSX fusion gene transcripts using an RNA sample extracted from the formalin-fixed paraffin-embedded tumor tissue, SYT break-apart rearrangement fluorescence in situ hybridization (SYT bar-FISH) successfully confirmed our diagnosis of SS for the tumor. Thus, SYT bar-FISH may be more suitable for the purpose of the molecular diagnosis of SS than conventional RT-PCR when using archival formalin-fixed paraffin-embedded tissue specimens.