[Primary Rectal Mesenteric Neuroendocrine Tumor G2-A Case Report].

An 81-year-old man with acute appendicitis was referred to our hospital. Abdominal computed tomography(CT)incidentally revealed a 53-mm mass in the left mesorectum. After a laparoscopic appendectomy, further investigation of the rectal mesenteric tumor was performed. Colonoscopy revealed an extrinsic compression of the lower rectum, and endoscopic ultrasound-guided fine-needle aspiration revealed a grade 2 neuroendocrine tumor(NET). A retrospective review of a CT scan performed 11 years earlier at another hospital revealed a solitary 13-mm mass in the same region of the left mesorectum, without continuity with the rectal wall. These findings therefore suggested that the primary rectal mesenteric NET had grown slowly over time. We performed laparoscopic low anterior resection, and the patient was recurrence-free at 6-month follow-up. Although primary mesenteric neuroendocrine tumors are rare, they should be considered in the differential diagnosis of primary mesenteric tumors.