Resection of a Neuroendocrine Tumor that Was Difficult to Diagnose Before Surgery: A Case Report

Abstract

A 76-year-old woman was referred to the Department of Gynecology of our hospital on account of an enlarging left ovarian tumor. Imaging suggested a tumor of the small intestine. Another tumor was newly found at a site between the perihilar bile duct and distal bile duct, close to a merger of three ducts. Since the bile duct tumor could either be a metastasis or primary bile duct cancer, we referred the patient to the Department of Surgery. CT and MRI suggested that the lesion was a solid tumor, and PET-CT showed accumulation. Based on these findings, surgery was performed for the original lesion (ovarian or small-intestinal tumor) and the newly found lesion (metastasis to the bile duct or primary bile duct cancer). An intraoperative biopsy revealed that the ovarian tumor was benign. However, the bile duct tumor could be a well-differentiated adenocarcinoma because of the increased number of glandular cells. Therefore, the tumor was resected. A histopathological examination of the excised specimen suggested that the biliary mucosa was maintained, leading to a diagnosis of a submucosal tumor. Immunostaining was positive for synaptophysin and negative for chromogranin A. Based on these findings, the final diagnosis was an extrahepatic biliary neuroendocrine tumor (NET, G1). The patient has been followed up as an outpatient and has had no recurrence 7 years after surgery. We report this case with a literature-based discussion as a rare example of primary extrahepatic biliary NET that was diagnosed histopathologically and resected surgically.