MUC4 and intrahepatic cholangiocarcinoma: In another study, MUC1 and MUC4, which are also ligands for RTK ERBB2 [46], were markedly upregulated in 81% (22/27) and 37% (10/27) of patients with MF-ICC, respectively, who displayed poorer prognoses than patients with IG-ICC or PI-ICC.