MUC5AC and intrahepatic cholangiocarcinoma: The subgroup of ICC with low or negative β4 and β6 integrin expression in the present study was characterized by peripheral localization, mass-forming gross types, poor mucin production, and luminal expression of EMA, indicating partial resemblance to the peripheral small bile duct type defined by Aishima et al. [22], the cholangiolar type identified by Liau et al. [10], and the mixed-ICC type described by Komuta et al. [9].