We report a 46-year-old woman with a systemic lupus erythematosus complicated with a lupus panniculitis. The patient developed initial deep breast nodules secondarily completed by superficial erythematosus and keratotic cutaneous lesions. Neoplasia was ruled out by X-ray and echographic investigations. Both subcutaneous and skin biopsies were consistent with the diagnosis of lupus mastitis. Lupus mastitis is a form of lupus panniculitis seldom associated with systemic lupus. A breast neoplasia should be ruled out by appropriate investigations and deep biopsies. The first-line treatment is based on antimalarial drugs.