MUC5AC and cholangiocarcinoma: Since these characteristics were similar to those of pancreatic IPMN of the branch duct type, they insisted that cystic and micropapillary lesions of peribiliary glands may have neoplastic features and might represent a precursor of biliary epithelial neoplasms, including IPNB of “the branch duct type.” Cardinale et al. [52] suggested that biliary stem/progenitor cells located in the peribiliary glands might be implicated in the carcinogenesis of mucin-producing cholangiocarcinomas.