||Bile duct carcinoma（cholangiocarcinoma）remains an intractable malignancy and is clincially detectable at the advanced stage in a majority of cases. Histologically, this carcinoma shows usually tubular and/micropapillary adenocarcinoma with variable fibrous stroma. Recently, two types of pre-neoplastic or early neoplastic lesions of bile duct carcinoma have been proposed in WHO 2010 tumor classification：biliary intraepithelial neoplasm（BilIN）and intraductal papillary neoplasm of bile duct（IPN-B）. BilIN is a flat lesion and recognizable microscopically, and is graded into BilIN-1（low grade）, BilIN-2（intermediate grade）, and BilIN-3（high grade）according to the atypia. BilIN is frequently found in the bile ducts around carcinoma and also in chronic biliary diseases such hepatolitahisis which is occasionally associated with cholangiocarcinoma. BilIN-3 is regarded to be followed by invasion of carcinoma into the surrounding tissue. IPN-B is a grossly visible intraductal papillary lesion in variably dilated bile duct lumen and is histologically graded into low, intermediate and high grade according to their atypia, and show four phenotypes（pancreatobiliary, gastric, intestinal and oncocytic）. IPN-B of high grade is associated with an invasion into the surrounding tissue. IPN-B occur in an apparently normal bile duct and also in chronic biliary diseases such as hepatolithiasis and liver fluke infection. In this symposium, characteristic histological and immunohistochemical features and also molecular abnormalities of these lesions will be presented.