Primary Intra-abdominal Synovial Sarcoma

We report a case of primary intra-abdominal synovial sarcoma of the omentum in a 66-year-old man hospitalized for intermittent abdominal fullness for 1-2 months and tenesmus for 2 weeks. The patient had a palpable mass that was solid, hard and with well-defined thickness within his abdomen. A huge heterogeneous mass lesion over the middle abdomen that started from S2, S3 of the liver to the transverse colon was shown on abdominal computed tomography. The major cell types of the tissue mass were confirmed to be spindle and epithelial cells, which was consistent with biphasic synovial sarcoma according to pathologic and immunohistochemical findings.