We report a case of mastitis showing bizarre calcifications in a systemic lupus erythematosus (SLE) patient. A 34-year-old woman had suffered from SLE for 12 years. Initial mammogram showed global asymmetry and extensive linear branching casting calcifications with ductal distribution in the left breast; the image had the appearance of a ductogram. Sonogram showed multiple calcifications without formation of a mass in the left breast. At 5-year follow-up, mammogram revealed large, coarsely conglomerated calcifications in the left breast. The clinical and radiological diagnosis of lupus mastitis was made.