Breast cancer is heterogeneous and involves both genetic and environmental factors, and it can be divided into three groups according to the molecular and histological characteristics: hormone receptor (estrogen receptor (ER+) or progesterone receptor (PR+)), human epidermal receptor 2 (HER2+) and triple-negative (ER−, PR−, and HER2−) breast cancer. The gene discussed is PGR; the disease is breast cancer.