Clinical, echographic and radiological findings were highly suggestive of breast carcinoma. A fine-needle aspiration biopsy was inconclusive, due to the firmness of the mass, and a core needle biopsy was not performed. A wide local excision was performed, and the histopathological diagnosis was "sclerosing lymphocytic mastitis".

The reported case of sclerosing lymphocytic mastitis is not associated with type I diabetes or autoimmune disease, as often occurs. Core biopsy is the most indicated method for establishing the diagnosis and it can eliminate the need for more aggressive procedures.