title: IgG4-related mastitis, a rare disease, can radiologically and histologically mimic malignancy.
abstract: IgG4-related disease (IgG4-RD) is characterised by high serum concentrations of IgG4, dense lymphoplasmacytic infiltrates, storiform fibrosis and increased IgG4-positive plasma cells in tissues. This systemic disease occurs in various organs metachronously, but IgG4-related mastitis appears extremely rare. We report a case of IgG4-related mastitis, radiologically considered to represent breast cancer mainly composed of intraductal component and requiring histological differentiation from mucosa-associated lymphoid tissue (MALT) lymphoma. The breast mass disappeared with steroid therapy. When patients have a breast mass, regardless of the presence or absence of IgG4-RD, IgG4-related mastitis should be considered in addition to breast cancer. If histological findings show dense lymphoplasmacytic infiltrates, IgG4-related mastitis should be suspected in addition to malignant lymphoma, and lack of monoclonality should be confirmed. To avoid unnecessary surgery or chemotherapy, knowledge and accurate diagnosis of the entity of IgG4-related mastitis is necessary.
authors.affiliation: Department of Pathology, Tokyo Metropolitan Komagome Hospital, Bunkyo-ku, Tokyo, Japan.
authors.forename: Rin
authors.initials: R
authors.lastname: Yamada
authors.affiliation: Department of Pathology, Tokyo Metropolitan Komagome Hospital, Bunkyo-ku, Tokyo, Japan.
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Horiguchi
authors.affiliation: Department of Breast Surgery, Tokyo Metropolitan Komagome Hospital, Bunkyo-ku, Tokyo, Japan.
authors.forename: Toshinari
authors.initials: T
authors.lastname: Yamashita
authors.affiliation: Department of Internal Medicine, Tokyo Metropolitan Komagome Hospital, Bunkyo-ku, Tokyo, Japan.
authors.forename: Terumi
authors.initials: T
authors.lastname: Kamisawa
mesh_terms: D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008413:Mastitis / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000473:pathology; D035583:Rare Diseases / Q000097:blood / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology; D013256:Steroids / Q000627:therapeutic use; D016896:Treatment Outcome
chemical_list: D007074:Immunoglobulin G; D013256:Steroids