Precancerous changes of extrahepatic bile ducts: biliary intraepithelial neoplasia and intraductal papillary neoplasm of the bile duct

Stenosis of extrahepatic bile ducts is a significant diagnostic problem in clinical practice. Up to 40% of extrahepatic bile duct stenoses are due to biliary intraepithelial neoplasia (BilIN) and intraductal papillary neoplasm (IPNB). The risk of developing cholangiocellular carcinoma against the background of BilIN and IPNB increases 160 times. The mutation of the KRAS gene has been shown to be the predictor of the transition of BilIN and IPNB to cholangiocellular carcinoma. Histological examination of biopsy material plays a crucial role in diagnosing stenosis. There have already been established criteria for assessing the degree of dysplasia in BilIN and IPNB, IPNB subtypes, and the most common and characteristic mutations in BilIN and IPNB. Moreover, immunohistochemical markers were recommended to determine the type/subtype of stenosis and assess the degree of epithelial dysplasia. Until now, lesions of extrahepatic gallbladder as a cause of stenosis or precancerous processes are one of the most pressing topics in hepatopancreatobiliary pathology. Thus, at this stage, it is necessary to develop simple algorithms for histological diagnosis, identify and introduce into practice additional methods of morphological research. Keywords: stenosis, biliary intraepithelial neoplasia, intraductal papillary neoplasm, dysplasia, mutations, immunohistochemical diagnosis