[A case of rectal gastrointestinal stromal tumor (GIST) locally resected after long-term chemotherapy with imatinib mesylate].

We report a case of gastrointestinal stromal tumor (GIST) locally resected after long-term chemotherapy with imatinib mesylate. A 78-year-old woman was diagnosed with GIST in the lower rectum on screening colonoscopy for anemia. The tumor was 7 cm in diameter, and the anal sphincter was considered to be difficult to preserve due to the extent of the tumor. The patient refused surgery, so she was administered imatinib mesylate chemotherapy. The medication was continued for 5 years without any major adverse events, and the status of the tumor was stable. Five years later, she underwent transanal local resection for anal prolapse and incarceration of the tumor. Pathological findings revealed a 7 cm sized high-risk GIST. The long-term stable status of the tumor was maintained, and the anal function was preserved by the local resection.