Clinicopathologic significance of the intraductal papillary neoplasm of the bile duct

Abstract

Intraductal papillary neoplasm of the bile duct (IPNB) is a precancerous or early-stage bile duct carcinoma composed of high columnar to cuboidal tumor cells growing in the intrahepatic and extrahepatic bile ducts with a marked papillary to villous structure centered in the thin fibrovascular stalks. IPNB is classified according to the degree of cytoarchitectural atypia into low grade and high grade. High-grade IPNB corresponds to intraepithelial carcinoma. IPNB was reported as a counterpart to pancreatic intraductal papillary mucinous neoplasm (IPMN) and is similar to pancreatic IPMN; it can be classified into four phenotypes according to the mucin-producing expression patterns: pancreatobiliary, intestinal, gastric, and oncocytic types. However, a consensus on the disease concept has not been fully accepted because it occurs less frequently than pancreatic IPMN, has fewer cases with mucus production, and involves two organs (liver and the extrahepatic bile ducts). This review focuses on IPNB's clinicopathological feature and the operational issues faced by clinicians and pathologists.