A 68-year-old man showed a 10-mm, red-tinted, flat, depressed lesion in the descending limb of the duodenum on esophagogastroduodenoscopy (EGD) for periodic follow-up after H.pylori eradication. Biopsy revealed an adenocarcinoma with low-grade atypia ; therefore, we adopted a wait-and-watch policy. EGD after 5 years revealed that the ulcer diameter had increased to 20 mm ; biopsy revealed an adenocarcinoma with partial high-grade atypia. We performed endoscopic treatment. Given the tumor diameter, gross appearance, and lesion biopsy findings, we performed endoscopic submucosal dissection. On pathological examination, the lesion was 19×19 mm and was accompanied by a highly differentiated intramucosal carcinoma within the adenocarcinoma ; the resection margins were negative. In Japan, there is no standard treatment for duodenal epithelial tumors, and a wait-and-watch policy is often adopted for adenocarcinomas with low-grade atypia and diameters of ≦10 mm, owing to the complication rates of endoscopic treatment. However, as in this case, where the lesion exhibits marked growth and high-grade atypia on pathology, endoscopic resection is necessary.
