IgG4-related mastopathy: A case report and literature review.

IgG4-related sclerosing disease (IgG4-RD) occasionally involves breast entity, which is often difficult to distinguish from malignant tumor, as both radiologically resembles. We report a case of a breast mass diagnosed as IgG4-related mastopathy (IgG4-RM) through needle biopsy, which responded well to glucocorticoid therapy. Unnecessary excision should be avoided.