IgG4-related sclerosing disease has been recognized as a systemic disease entity characterized by an elevated serum IgG4 level, sclerosing fibrosis, and diffuse lymphoplasmacytic infiltration with the presence of many IgG4-positive plasma cells. Clinical manifestations are apparent in the pancreas, bile duct, gall bladder, lacrimal gland, salivary gland, retroperitoneum, kidney, lung, breast, thyroid, and prostate. Immunohistochemical analyses in the case of IgG4-related sclerosing disease not only exhibit significantly more than normal IgG4-positive plasma cells in affected tissues but also significantly higher IgG4/IgG ratios (typically > 30%).