Expression of MUC1 and MUC2 mucin antigens in intrahepatic bile duct tumors: Its relationship with a new morphological classification of cholangiocarcinoma

Our previous immunohistochemical study on intrahepatic bile duct tumors sho wed that invasive cholangiocarcinoma (ICC) with a poor outcome expressed MU C1 mucin but was negative for MUC2 mucin, whereas bile duct cystadenocarcin oma (BDCC) with a favorable outcome was MUC1 negative and MUC2 positive. In the present study, ICC was further subdivided into 2 subtypes: intraductal growth type and/or periductal infiltrating type (ICC-IP) and mass forming type (ICC-M). The survival of patients with BDCC or ICC-TP is significantly better than that of patients with ICC-M, We examined these subtypes (ICC-I P and ICC-M) and BDCC for their expression of MUC1 mucins of different glyc oforms. ICC-M showed significantly higher MUC1 expression rates (90%, 95%, and 85% positive rates as measured with the DF3, MY.1E12, and MUC1-Glycopro tein antibodies, respectively) than BDCC and ICC-IP (14% and 33%, 58% and 5 8%, and 0% and 50% positive respectively, as measured by the same antibodie s). In contrast, BDCC (86% positive) and ICC-IP (67% positive) showed signi ficantly higher MUC2 expression rates than ICC-M (25% positive) as measured with the anti-MRP antibody. Thus, the immunohistochemical staining pattern of ICC-IP resembled the pattern of BDCC more than they resembled ICC-M, In general, MUC1 expression is associated with poor patient outcome, irrespec tive of the glycosylation status. In particular, high expression of more si alylated forms of MUC1 mucins was correlated with poor survival. In contras t, expression of non-sialylated MUC2 mucin is a favorable prognostic indica tor. These results suggest that ICC-IP is a different entity from ICC-M, Th is reclassification may have value in determining prognosis and treatment m ethod.