Gastrointestinal stromal tumor of the lesser omentum: report of a case.

We describe herein an extremely unusual case of a gastrointestinal stromal tumor (GIST) of the lesser omentum. A 45-year-old man was admitted to our hospital with an intra-abdominal mass that was subsequently misdiagnosed as a submucosal tumor of the stomach. The tumor arose from the lesser omentum and was removed without difficulty. Histologically, the tumor was composed of spindle-shaped cells with an interlacing bundle pattern, and immunohistochemical examination showed that it was positive for myeloid stem cell antigen (CD34), but negative for HHF35 and S-100 protein. These findings were consistent with a GIST lacking myogenic features and neural attributes. The patient had an uneventful postoperative course, and was free of recurrence when last seen 11 months after his operation.