Colonoscopy in a 33-year-old man showed a submucosal tumor with a depression, 13 mm in size, in the lower rectum. Biopsy examination revealed NET. Endoscopic ultrasound showed that the muscularis propria was preserved and the lesion was localized to the submucosal layer. We selected ESD method for complete resection. Immunohistochemistry revealed synaptophysin (+), chromogranin A (+), CD56 (+), and Ki-67index 2%, and he was diagnosed with NETG1. The lesion remained in the submucosal region, and the margin was negative. Lympho-vascular invasion was not recognized. The cell proliferation ability was low. From these findings, we considered that the risk of metastasis was low and did not perform additional resection. Five years have passed without recurrence. This case was able to avoid surgical excision by appropriate treatment and detailed histopathological diagnosis.
