Immunoglobulin G4-related sclerosing mastitis: an unexpected diagnosis for a breast mass.

Immunoglobulin G4-related disease is an immune-mediated condition comprised of a number of various disorders sharing unique pathologic, serologic, and clinical features. Diagnosis of immunoglobulin G4-related sclerosing mastitis is challenging as the clinical and imaging findings mimic breast malignancies or other types of inflammatory mastitis. Herein, we describe a case of a female patient with a painless palpable mass in her right breast. An excisional core biopsy led to the rare diagnosis of immunoglobulin G4-related sclerosing mastitis, and the patient received steroid treatment for a month. To date, the patient has remained disease-free without any recurrence. As immunoglobulin G4-related sclerosing mastitis is a very rare disease, further studies are needed to reach conclusions about the pathogenesis, diagnosis, and treatment of this entity.