Abstract
A 78-year-old man consulted a nearby clinic because of melena, and was admitted to the hospital. Diagnostic imaging revealed a submucosal tumor with central ulceration in the left wall of the lower rectum. A Miles' operation was performed following the diagnosis and the tumor was 47×40×35mm in size. Histological examination of the resected specimen showed the tumor to be composed of spindle shaped cells with a few mitosis. Tumor cells were positive for c-kit and CD34, negative for α-SMA and S-100 by immunohistochemical examination. We diagnosed this tumor as gastrointestinal stromal tumor (GIST), uncomitted type, malignant. He has been well for 2 years 7 months after operation without evidence of recurrence. GIST of the rectum with immunohistochemically positive for c-kit is rare with only 18 reported cases in the Japanese literature. This immunohistochemical evaluation with c-kit has been essential for the diagnosis of GIST.
