Intrahepatic biliary papillomatosis associated with malignant transformation: report of two cases and review of the literature.

Biliary papillomatosis (BP) is a rare disease characterized by multiple numerous papillary adenomas in both the intrahepatic and extrahepatic biliary tree. Due to its high recurrence rate and frequent transformation to malignancy, BP should not be considered a benign disease, and a radical resection with an adequate resection margin is advocated in cases of localized intrahepatic biliary papillomatosis. Since BP is a rare disease and its clinical features and outcomes are not well known, it's really difficult to diagnose the disease before operation.