[A Case of Appendiceal Neuroendocrine Tumor Diagnosed after Appendectomy].

A 25-year-old woman visited our hospital with a complaint of right lower abdominal pain. As a result of the examination, she was diagnosed as having acute appendicitis. After conservative treatment, we planned an elective surgery. At 3 months after discharge, laparoscopic appendectomy was performed. We found a mass of 10mm in diameter at the body of the appendix. Histopathological examination revealed the proliferation of heteromorphic cells with small round nuclei. It was positive for chromogranin A and synaptophysin in immunostaining, so we made a diagnosis of NET G1. Tumor cells infiltrated beyond the intrinsic muscle layer, but no vascular invasion was observed, and the margin was negative. In accordance with the guidelines, we followed up the patient with imaging examination and did not find any signs of recurrence.