Selection of alternative treatments and predictive factors for breast cancer prognosis that is currently widely used include estrogen receptor-positive (ER+), carcinoembryonic antigen (CEA), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), urokinase plasminogen activator (uPA), plasminogen activator inhibitor 1 (PAI-1). This evidence concerns the gene ESR1 and breast cancer.