Abstract
BACKGROUND: A rectal neuroendocrine tumor (rNET) is a malignant tumor originating from neuroendocrine cells. Currently, tumor size is the primary basis for assessing tumor risk. CASE SUMMARY: This article reports the case of a 46-year-old male patient who underwent a colonoscopy that found a 3 mm rectal polypoid bulge. The pathological examination of a sample collected with biopsy forceps revealed a neuroendocrine tumor. Further endoscopic submucosal dissection rescue therapy was used. The presence of lymphatic vessels indicated that the tumor had infiltrated the negative resection margin. The lesion was located in the distal rectum near the anal canal. Therefore, to ensure the patient's quality of life, follow-up observation was conducted after full communication with the patient. No tumor recurrence or distant metastasis has been found during the 13-mo follow-up after surgery. CONCLUSION: Despite the presence of lymphatic invasion and extremely small diameter rNETs in our case, this phenomenon may not imply a higher risk of distant lymph node and organ metastasis.