Male breast cancer after finasteride therapy for benign prostate hyperplasia

Finasteride has been used for the treatment of benign prostate hyperplasia (BPH) for years, but some side effects, including male breast cancer (MBC), have been reported. We report a case of breast cancer in a male patient who received finasteride therapy for BPH, and to our knowledge, our report is believed to be the first in Taiwan. The patient was a 59-year-old man who received finasteride therapy for BPH for 4 years. He found a palpable mass in his left breast 2 months prior to diagnosis. Ultrasound-guided core biopsy showed invasive ductal carcinoma. A simple mastectomy was performed followed by chemotherapy with tamoxifen.