Immature MUC5AC (detected by CLH2 antibodies) is upregulated in many BTC precursor neoplasms such as biliary intraepithelial neoplasia (BilIN), intraductal papillary neoplasm of the bile duct (IPNB), gallbladder dysplasia, biliary dysplasia, and intraductal papillary neoplasm of the liver (IPNL) [44,86,93,94,98,99,100,101]. The gene discussed is MUC5AC; the disease is gallbladder biliary intraepithelial neoplasia.