My approach to intraductal bile duct proliferations

Intraductal proliferations of the bile duct usually involve large bile ducts, and can occur in the intrahepatic, perihilar, and extrahepatic sites. Pre-invasive grossly detectable neoplasms are currently termed as intraductal papillary neoplasms of the bile duct (IPN-B). There is cytologic and architectural heterogeneity between and within these tumors. Based on morphologic differences between intrahepatic and extrahepatic IPN-B, the tumors can be subclassified into Type 1 and Type 2. These neoplasms show a spectrum from low-grade to high-grade dysplasia and can be associated with invasive carcinoma. The neoplasms can also be diagnosed in a biliary biopsy. The prognosis of malignancy arising in IPN-B is better than other cholangiocarcinomas. Molecular changes usually involve common genetic alterations in KRAS, CDKN2A, and TP53 genes. Complete surgical resection is curative in a non-metastatic setting.