A Case of Gastrointestinal Stromal Tumor of the Rectum Involving a Buttock Tumor

Abstract

A 62-year-old man was admitted to our hospital due to a buttock tumor. After imaging examinations, the tumor was resected based on a diagnosis of myoma or sarcoma. At resection, the specimen was histologically diagnosed as gastrointestinal stromal tumor (GIST), malignant. A Miles operation was conducted following diagnosis. Histological examination of the resected specimen showed the tumor consisted of spindle-shaped cells. Immunohistochemical testing was negative for S-100, and positive for smooth-muscle actin, CD34, and c- kit, making this tumor a malignant smooth muscle GIST. Thereafter, 11 rectal GIST cases were reported in Japan. We reviewed the total of 12.