Primary Synovial Sarcoma of the Kidney: A Case Report and Literature Review

Synovial sarcoma is a rare renal neoplasm that is not easy to diagnose unless SYT-SSX fusion transcripts are identified. We report here on a case of primary renal synovial sarcoma in a 35-year-old woman. A mass was discovered by accident in the lower part of the right kidney when ultrasonography was performed, and it was removed via radical nephrectomy. Grossly, the tumor was a homogeneously tan-brown soft mass that measured 4.5 x 3.2 x 3.0 cm, and it was encircled by a well-defined cystic space. The lesion exhibited hypercellularity of the oval or short spindle cells that were arranged in various solid sheets or intersecting fascicles. Immunohistochemically, the tumor showed diffuse positivity for vimentin, bcl-2 and CD99, and it showed focal positivity for epithelial membrane antigen. The SYT-SSX fusion transcripts were detected by reverse transcription-polymerase chain reaction (RT-PCR). Synovial sarcoma should be considered in the differential diagnosis when a spindle cell neoplasm is encountered in the kidney.