Hilar bile duct neuroendocrine tumor: an incidental finding

Abstract

Background: Neuroendocrine tumors (NETs) usually occur in the gastrointestinal system, but very rarely arise from the bile duct, especially from the hilar bile duct where they account for only 0.1%–0.4% of primary NET sites. Here we present an incidentally found bile duct NET. Methods: A 54-year-old Caucasian male with a history of non-alcoholic steatohepatitis, micro- nodular cirrhosis and psoriasis was admitted for increased generalized swelling which improved with diuresis. An acceptable liver donor was found during admission after which patient underwent liver transplantation. Results: The explant liver (1026 g) grossly was tan brown and diffusely nodular with attached tan-pink gallbladder. Section of the hilum adjacent to the resection margin revealed an incidental, completely resected, 3 mm well circumscribed, well-differentiated tumor adherent to the wall of the hilar bile duct. Microscopy revealed a grade 1, well-differentiated NET exhibiting mitosis. KI-67 index was less than 2% positive. Synaptophysin and chromogranin highlighted tumor cells. PAS-D and iron stains were negative. Vascular invasion was not found. Conclusion: Primary bile duct NETs are exceedingly rare and difficult to identify preoperatively. Diagnosis is often made postoperatively after histological and immunohistochemistry specimen analysis. Bile duct NETs tend to display an indolent behavior. The best predicator of aggressive behavior is tumor size greater than 2 cm. The treatment of choice is complete surgical excision. An extensive literature review revealed approximately 70 cases of well-differentiated NETs of extrahepatic bile ducts since the first reported case in 1959. A multidisciplinary approach for diagnosis of these tumors, continued reporting, and long term follow-up of patients is crucial for gathering data regarding the risk of recurrence to guide appropriate management.