A 51-year-old male was admitted to our hospital for the treatment of a laterally spreading tumor in the rectum. A protrusion with bridging folds, which suggested a SMT was found in the second part of the duodenum by screening endoscopy for preoperative check up. The lesion had slightly reddish and erosive surface, and several biopsy specimens were taken from the eroded area. The diagnosis of carcinoid tumor was made, since these specimens demonstrated positive reactions to chromogranin A, synaptophysin and Grimelius stain. Endoscopic ultrasography revealed that the tumor was mainly located in the submucosal layer, and the tumor size was 15mm in diameter. It is reported that the risk of metastasis depends on its size, and since large tumors more than 10mm are judged to be high risk, the patient underwent laparotomy. Operative findings showed no obvious metastatic lesions in the liver, no lymph node swelling or disseminated lesions in the peritoneum, therefore partial duodenectomy was performed. The resected specimen revealed that the tumor was originated from the submucosa and the surgical margin was negative for carcinoid.
