Background and Study Aim: Recently, immunohistochemistry has shown numerous IgG4-positive plasma cells in a subset of Hashimoto’s thyroiditis (HT), and this type of HT (IgG4 HT) appears to be a subtype of IgG4-related sclerosing disease. However, little is known about the distribution pattern of plasma cells in IgG4 thyroiditis. To clarify the distribution pattern of IgG4-positive plasma cells,...