Intraductal papillary neoplasm of the bile duct: The new frontier of biliary pathology

Abstract

Intraductal papillary neoplasms of the bile duct (IPNBs) represent a rare variant of biliary tumors characterized by a papillary growth within the bile duct lumen. Since their first description in 2001, several classifications have been proposed, mainly based on histopathological, radiological and clinical features, although no specific guidelines addressing their management have been developed. Bile duct neoplasms generally develop through a multistep process, involving different precursor pathways, ranging from the initial lesion, detectable only microscopically, i.e. biliary intraepithelial neoplasia, to the distinctive grades of IPNB until the final stage represented by invasive cholangiocarcinoma. Complex and advanced investigations, mainly relying on magnetic resonance imaging (MRI) and cholangioscopy, are required to reach a correct diagnosis and to define an adequate bile duct mapping, which supports proper treatment. The recently introduced subclassifications of types 1 and 2 highlight the histopathological and clinical aspects of IPNB, as well as their natural evolution with a particular focus on prognosis and survival. Aggressive surgical resection, including hepatectomy, pancreaticoduodenectomy or both, represents the treatment of choice, yielding optimal results in terms of survival, although several endoscopic approaches have been described. IPNBs are newly recognized preinvasive neoplasms of the bile duct with high malignant potential. The novel subclassification of types 1 and 2 defines the histological and clinical aspects, prognosis and survival. Diagnosis is mainly based on MRI and cholangioscopy. Surgical resection represents the mainstay of treatment, although endoscopic resection is currently applied to nonsurgically fit patients. New frontiers in genetic research have identified the processes underlying the carcinogenesis of IPNB, to identify targeted therapies.

Keywords: Intraductal neoplasm of the bile duct, Bile duct neoplasms, Cholangiocarcinoma, Intraductal papilloma, Classification, Treatment

Core Tip: Intraductal papillary neoplasms of the bile duct are rare premalignant lesions, which are especially prevalent in East Asia. Due to the lack of specific guidelines addressing their management, recent subclassification of types 1 and 2 clarifies several aspects, particularly histopathological, clinical and prognostic features. Magnetic resonance imaging and cholangioscopy occupy a central role in diagnosis and treatment. Surgery is the most appropriate treatment, yielding optimal results in terms of survival, although endoscopic techniques have been used, particularly in nonsurgically fit patients. Lastly, recent genetic research has focused on identifying targeted therapies acting on the stepwise progression of neoplastic biliary epithelium.