Different expression patterns of mucin core proteins and cytokeratins during intrahepatic cholangiocarcinogenesis from biliary intraepithelial neoplasia and intraductal papillary neoplasm of the bile duct—an immunohistochemical study of 110 cases of hepat

Background/Aims Two types of neoplastic lesions preceding invasive intrahepatic cholangiocarcinoma (ICC) are identified: a flat-type neoplastic lesion called ‘biliary intraepithelial neoplasia (BilIN)’ and an intraductal papillary neoplasm of the bile duct (IPN-B). Multi-step carcinogenesis has been suggested in both lesions, although phenotypic changes during this process remain unclarified. Methods We immunohistochemically examined expression patterns of MUC1, MUC2, MUC5AC, cytokeratin 7 (CK7), and CK20 in BilIN, IPN-B, and ICC in 110 cases of hepatolithiasis. Results Thirty-seven cases of ICC in hepatolithiasis were divided into 18 tubular adenocarcinomas with BilIN, 10 tubular adenocarcinomas with IPN-B and nine colloid carcinomas with IPN-B. Carcinogenesis via BilIN was characterized by MUC2−/CK7+/CK20−with increasing MUC1 expression. IPN-B was characterized by the intestinal phenotype (MUC2+/CK20+), and carcinogenesis leading to tubular adenocarcinoma was associated with increasing MUC1 expression and that to colloid carcinoma with MUC1-negativity. Pathological stages of tubular adenocarcinoma of ICC with BilIN or IPN-B were more advanced than those of colloid carcinoma with IPN-B. Conclusions Immunophenotypes of MUCs and cytokeratins might characterize three cholangiocarcinogenetic pathways in hepatolithiasis. Increased expression of MUC1 in BilIN and also IPN-B is associated with tubular adenocarcinoma, while colloid carcinoma in IPN-B is characterized by MUC1-negativity and less advanced pathologic stages.