This course will provide a diagnostic framework for evaluating selected inflammatory, neoplastic, and congenital disorders of the biliary system, with emphasis on clinicopathologic correlation. The course is designed for practicing surgical pathologists and upper level pathologists in training. Three general topics will be presented: inflammatory conditions, primarily immune-mediated, affecting the intrahepatic and extra-hepatic bile ducts, epithelial neoplasms of the intra- and extra-hepatic bile ducts, and the group of congenital disorders of the biliary tree known as "ductal plate malformations". Inflammatory conditions to be discussed include primary biliary cirrhosis, primary sclerosing cholangitis, autoimmune cholangiopathy and overlap syndromes, adult idiopathic ductopenia, microbial cholangiopathies in the immunodeficient patient, drug-induced bile duct injury, and post-transplant cholangiopathies. Classification and diagnostic terminology of benign and malignant biliary epithelial tumors will be discussed, with coverage of clinical features, epidemiology, and associated conditions. Case studies will be used to illustrate diagnostic approaches to disorders of the biliary system. Discussion will emphasize using microscopic features to generate a differential diagnosis, and incorporation of clinical information and laboratory studies in narrowing the differential diagnosis. A limited number of loan sets of glass slides will be available for advance mailing. All participants will be mailed a set of transparencies for retention after the meeting. A detailed syllabus will be distributed at the course. (Last Scheduled Presentation)