A 73-year-old woman noticed a mass in her right breast about 1 year ago and consulted our hospital for an enlarged mass of about 10 cm in diameter.She was diagnosed with locally advanced triple negative breast cancer, and we initiated S-1 treatment as neoadjuvant chemotherapy.After 4 chemotherapy courses, computed tomography showed that the primary tumor had shrunk.Therefore, right mastectomy and axillary dissection were performed, and UFT was administered after surgery.She is currently alive with no recurrence 18 months after surgery.