Primary Well-Differentiated Neuroendocrine Tumor of the Common Hepatic Duct

Well-differentiated neuroendocrine tumors (WD-NETs) of the extrahepatic bile duct (EHBD) are exceedingly rare. Their histopathologic features are variable and lack defined prognostic correlates in the current literature. We describe a 69-year-old male patient with a primary WD-NET at the bifurcation of the common hepatic duct. On initial presentation, the patient was found to have abnormal liver enzymes. Subsequent imaging revealed a mass in the common hepatic duct concerning for cholangiocarcinoma. He underwent extrahepatic biliary resection and formal portal lymphadenectomy. Findings on postoperative histologic evaluation were consistent with a WD-NET, but revealed both favorable and unfavorable pathologic features. This juxtaposition of pathologic features, compounded by the variable behavior of WD-NETs between different anatomic primary sites, highlights the need for further characterization and grading criteria specific to this tumor. In detailing this patient, we contribute to the important number of case reports necessary to inform future guidelines. Reporting of such tumors should continue until guidelines for risk stratification, management, and surveillance of EHBD WD-NETs can be established.