A 68-year-old woman with a 5-year history of an untreated left breast tumor presented to our hospital. She was admitted for untreated diabetes and severe anemia. The cause of the anemia was bleeding from the tumor, and she was referred to our department. She was diagnosed with T4bN0M0, stage IIIb breast cancer. First, we initiated hormonal therapy. However, the tumor did not decrease in size. We then administered chemotherapy. The tumor markedly decreased in size, and mastectomy and axillary lymph node dissection were performed. The response was a pathological complete response. She is currently undergoing hormonal therapy at the time of this writing.