Immunohistochemistry of IgG4 can help subclassify Hashimoto's autoimmune thyroiditis

IgG4‐related sclerosing disease has been recently recognized as a systemic disease entity characterized by an elevated serum IgG4 level, sclerosing fibrosis and diffuse lymphoplasmacytic infiltration by many IgG4‐positive plasma cells. Similar histopathological features have often been noted in the fibrous variant of Hashimoto's autoimmune thyroiditis, but thyroid gland involvement has been only briefly mentioned with regard to IgG4, and no...