Neoplastic premalignant pancreatobiliary lesions: current update on the spectrum of lesions and their imaging appearances.

Common pancreatobiliary epithelial malignancies such as pancreatic ductal adenocarcinoma, cholangiocarcinoma and gallbladder carcinoma have poor prognosis. A small but significant portion of these malignancies arise from mass-forming grossly and radiologically visible premalignant epithelial neoplasms in the pancreatobiliary tree. Several lesions, including a few recently described entities, fall under this category and predominantly include papillary epithelial lesions with or without mucin production. These include common lesions such as intraductal papillary mucinous lesions (IPMN) in pancreas and less common to rare lesions such intraductal papillary neoplasms of the bile ducts (IPNB), pancreatic and biliary intraductal oncocytic papillary neoplasms (IOPN) and intraductal tubulopapillary neoplasms (ITPN), intracholecystic neoplasms (ICN) in the gallbladder, intra-ampullary papillary-tubular neoplasms (IAPN) in the ampulla and mucinous cystic neoplasms in the pancreas, biliary tree and gallbladder. These lesions have an excellent prognosis before malignant transformation and even with malignant transformation, often fare better than the conventional malignant counterparts. These lesions have characteristic histologic, radiologic, and molecular characteristic features. Several of these neoplastic lesions are associated with field-effect phenomenon which means that in presence of even one of these lesions, the entire background ductal epithelium is at risk of developing synchronous or metachronous malignancies. Awareness of these lesions and their imaging appearances as well as utilization of relevant molecular diagnostics can help practicing radiologists and clinicians improve patient outcomes by detecting early and treating or surveilling such lesions before malignant transformation or before metastatic dissemination.