A 65-year-old male had been followed for diabetes mellitus and angina pectoris, and his stools were positive for occult blood at the annual physical examination. Upper GI endoscopy revealed a duodenal polyp greater than 3cm in diameter. Its shape was submucosal pedunculated type. After biopsy, he noted continuing tarry stools and was admitted because of dizziness. Reupper GI endoscopy revealed that the polyp had changed its shape in a short term. Its stalk was thick and twisted and its top was lobulated and ulcerated. The size was 3×4cm in diameter. We diagnosed that tarry stool was originated from bleeding of these erosions and performed endoscopic hemostasis with clips. Endoscopic polypectomy was difficult because of its large size and not confirming the diagnosis. Therefore surgical resection was performed. Histological findings of the resected specimen showed Brunner's gland hyperplasia.
