A Case of 5 mm Rectal Neuroendocrine Tumor(NET)G1 with Lymph Node Metastasis at Additional Surgical Resection after EMR

We report the case of a patient who underwent additional surgical resection of a rectal neuroendocrine tumor(NET)G1 with a tumor diameter of 5 mm after endoscopic resection, and lymph node metastasis was observed. The patient was a 33- year-old woman. A lower gastrointestinal endoscopy was performed to examine the blood in the stool. A submucosal tumor of 5 mm in size was found in the rectum Ra, and endoscopic mucosal resection was performed. Pathological examination of the resected tissue revealed NET G1; HE staining revealed negative margins and no vascular invasion, but additional immunostaining revealed lymphatic invasion(Ly1a). Additional surgical resection was decided, and a laparoscopy-assisted low anterior resection D3 were performed. The surgical resection specimen showed no residual NET component in the rectum, but metastasis was found in one lymph node. The postoperative course of the patient has been uneventful, and the patient is currently undergoing without recurrence 6 months after the surgery. In the case of NET G1, it is important to search for detailed vascular invasion by immunostaining even in small lesions, and if vascular invasion is found, additional surgical resection should be considered.