[A Case of Rectal Neuroendocrine Tumor with a Major Axis of 10.7 mm with Lymph Node Metastasis].

The case is a 50-year-old woman. Colonoscopy performed by a local doctor for the purpose of stool occult blood positive revealed a 15 mm tumor in the lower rectum, biopsy showed chromogranin positive, synaptophysin positive, and Ki-67 index<1% showed a neuroendocrine tumor(NET), G1 was diagnosed and introduced. Colonoscopy revealed a smooth- surfaced circular hemispherical tumor with a lower edge 30 mm from the anal margin and 20 mm from the dentate line, and EUS showed 10.7×5.2 mm in layers 2 to 3. It was visualized as a well-defined hypoechoic tumor. Contrast-enhanced CT examination showed a 12×5 mm mass showing a contrast-enhancing effect, and no lymphadenopathy or distant metastasis was observed. Contrast-enhanced MRI showed no evidence of pelvic lymphadenopathy. Based on the above, it was diagnosed that NET, G1, and infiltration to the submucosa exceeding 10 mm. Although endoscopic resection as a diagnostic treatment was also an option, we determined surgical resection policy, therefore we performed laparoscopic rectal intersphincteric resection and upper D2 dissection. Histopathological findings showed a tumor of 11×8 mm infiltrating the submucosa( 5,000μm)with metastasis to the pararectal lymph nodes, and the diagnosis was T1b, N1, Ki-67 index 3%, Ly1, V1a, NET G2, pStage ⅢB. Her postoperative course was uneventful, and 6 months later, we performed her artificial anal closure. One year after the operation, there are frequent bowel movements but no fecal incontinence and she is alive without recurrence. For rectal NET with a tumor diameter of 10 mm or more, radical surgery with dissection is recommended because of the high risk of lymph node metastasis. In this case lymph node metastasis was observed surgical resection according to the above reason, but endoscopic resection was possible except that the preoperative size exceeded 10 mm to 0.7 mm and the distance from the anus was short, therefore it took some thought to decide the policy.