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Abstract: IgG4-related disease involving the liver and biliary tree exhibits variable morphological changes. The most common manifestation is sclerosing cholangitis characterized by pipe stem-like fibrosis of the wall and extensive inflammation. IgG4-related sclerosing cholangitis sometimes exhibits pseudo-tumourous exuberance around the hilar bile duct (inflammatory pseudotumour), radiological features of which are reminiscent of hilar cholangiocarcinoma. Another minor manifestation is IgG4-related chronic active hepatitis. Consistent with other manifestations of IgG4-related disease, pathological features include diffuse lymphoplasmacytic infiltration, irregular fibrosis typically in a storiform pattern, and moderate tissue eosinophilia. On immunostaining, not only the absolute number of IgG4-positive plasma cells but also the IgG4/IgG-positive ratio is dramatically increased. Pathologists need to be aware of this condition, as the diagnosis requires a multi-disciplinary approach, in which pathological examination has a critical role. [Copyright &y& Elsevier]