Lupus mastitis mimicking a breast tumor

Abstract Lupus mastitis represents a subset of breast‐limited lupus panniculitis, and occurs very rarely in patients with systemic lupus erythematosus. We report a case of a 33‐year‐old white woman with a previous history of systemic lupus erythematosus, complaining of an acute tenderness and pain in the right breast associated with localized skin erythema. Ultrasound and mammography reports from a private breast clinic, where she was scheduled for core needle biopsy, aroused suspicion of a breast tumor. Clinically the patient had a painful mass suggestive of an inflammatory lump with an abscess. Her double‐stranded DNA antibody level, white blood cell count and erythrocyte sedimentation rate (ESR) were increased; and her renal function was impaired and serology findings negative. All other laboratory tests were within the normal ranges. The patient underwent urgent surgical incision and excisional biopsy of the lesion, and histology revealed lupus mastitis. Lupus mastitis very rarely may appear as a breast lump and therefore presents a great diagnostic challenge for clinicians, occasionally for radiologists and rarely for pathologists.