Morphologic and molecular diagnostic criteria of malignancies in biliary strictures.

The differential diagnosis of benign and malignant biliary strictures is not always feasible and still represents a major diagnostic challenge, mainly due to the scarcity of the tissue retrieved for proper cytological or histopathological diagnosis. The present review focuses on morphological criteria in the diagnosis of biliary strictures, in the course of primary sclerosing cholangitis and other pathologies, starting from the limits of the cytological and histological evaluation, as well as the ancillary methodologies currently available in Pathology laboratories The current guidelines suggest fluorescence in situ hybridization for the analysis of chromosomes 3, 7, and 17 polysomies and deletion of the 9p21 locus; however, other more promising techniques are on the horizon for both patient care and research purposes, such as Next-Generation Sequencing, able to analyze multiple genes simultaneously in a cost-effective fashion. Lastly, the most recent approaches proposed in the literature for the differential diagnosis of biliary stricture are described, such as circulating tumor DNA, miRNAs, and DNA methylation, among others.