MUC6 and cholangiocarcinoma: MUC1 showed high expression in cholangiocarcinomas and cholangiocellular differentiated areas of cHCC-CCC [157,158,159], whereas MUC2 [158,159], MUC3 [158,159], MUC5/6 [159], MUC5AC [158], MUC6, and MUC7 [158] showed limited usefulness for further differentiation.