MUC2 and cholangiocarcinoma: In CCA, several aberrant glycans and glycoproteins are correlated with CCA progression, such as carbohydrate antigen 19-9, carcinoembryonic antigen, mucin (MUC)1, MUC2, MUC5AC, serum α1β-glycoprotein, and several lectin-binding glycans [12–17].