Primary gastric synovial sarcoma.

Synovial sarcoma is a malignant soft tissue neoplasm that may arise from a variety of sites in the human body. It is typically characterized by its biphasic histological pattern, but a monophasic type composed entirely of spindle cells also exists. The diagnosis of monophasic synovial sarcoma can be very challenging and often requires molecular diagnostic techniques, especially for tumors arising in rare locations such as the gastrointestinal tract. We report here the case of a 38-year-old woman with a primary gastric monophasic synovial sarcoma confirmed by reverse transcriptase polymerase chain reaction that revealed t(X;18) (SYT-SSX1) translocation. To our knowledge, only 11 synovial sarcomas arising in the stomach have previously been reported. The pathologic features, differential diagnoses, and clinical manifestations are discussed.