Primary synovial sarcoma of the kidney: Report of a case confirmed by molecular detection of the SYT-SSX2 fusion transcripts

We describe an unusual case of primary synovial sarcoma of the kidney. A 47-year-old woman had a tumor massively, replacing the right kidney. There were no primary extrarenal neoplastic lesions. Microscopically, the tumor was composed of a cellular proliferation of relatively uniform spindle-shaped cells having atypical spindle or oval nuclei arranged in fascicles with tumor necrosis, without epithelial areas. Immunohistochemically, a small number of the tumor cells were positive for epithelial markers such as cytokeratin and epithelial membrane antigen. The SYT-SSX2 fusion transcripts were detected by a reverse transcription-polymerase chain reaction (RT-PCR) using RNA extracted! from formalin-fixed, paraffin-embedded tissue. ETV6-NTRK3 fusion gene transcripts that result from t(12; 15)(p13;q25), which is characteristic of cellular congenital mesoblastic nephroma, were not demonstrated. To our knowledge, this is the ninth case of primary renal synovial: sarcoma. This case report indicates that synovial sarcoma should be taken into account for the differential diagnosis of renal spindle cell tumors and the molecular assay detecting the SYT-SSX2 fusion transcripts is useful for the final diagnosis of synovial sarcoma arising in an unusual location.