A 51-year-old woman with neurofibromatosis type 1 presented to our department for investigation of a left breast lump (50 x 50 x 30 mm); a mass in the right breast (40 x 40 x 20 mm) was also detected on physical examination. The lumps were suspected to be malignant based on physical examination and ultrasonography. Biopsy and frozen sections subsequently confirmed a diagnosis of bilateral invasive ductal carcinoma. A standard bilateral radical mastectomy was performed, followed by postoperative chemoendocrine therapy. Tumor recurrence has not been observed within the first 23 months following the surgery.