Pathological characteristics of intraductal papillary neoplasm of the bile duct

Abstract

Intraductal papillary neoplasm of the bile duct (IPNB) is a papillary neoplasm that can be recognized macroscopically residing inside bile duct. Microscopically, the neoplasm is composed of papillae with thin fibrovascular cores occasionally with tubular components, which shows various grades of atypia that is classified into low-grade, high-grade, and invasive. Invasive components show either tubular adenocarcinoma or mucinous carcinoma. Neoplastic papillae can be classified by morphological characteristics into four subtypes including gastric, intestinal, pancreatobiliary, and oncocytic, which corresponds to variations in intraductal papillary mucinous neoplasms of the pancreas. The Japan-Korea classification of IPNBs into type 1 and type 2 enabled to evaluate classic/typical IPNBs and atypical IPNBs, which is well associated with distinctive clinicopathological features including molecular aberrations and patients' prognosis.