A Case of KIT-negative Gastrointestinal Stromal Tumor of the Small Intestine Respond to Imatinib after Surgical Intervention

A 70-year-old male was admitted for gastrointestinal bleeding. Endoscopic examinations failed to detect the site of the bleeding, and a CT scan disclosed a single liver mass and several intra-abdominal tumors. The preoperative diagnosis was metastatic GIST with intestinal bleeding, and the segment of small intestine involved 70cm distal to the ligament of Treitz and some peritoneal disseminated masses were resected. The resected tumors were microscopically examined and classified as CD34+, c-kit-, SMA-, S100- GISTs. Treatment with 400mg of imatinib started 24 days later and positron emission tomography (PET) 7 days later showed a marked decrease in abdominal uptake compared with PET before treatment. Adverse effects were minimal and the patient. s disease has been stable during fifteen months since imatinib was started.