Several clinicopathological factors are known to be important in the prognosis of breast cancer patients, including nodal status [12, 13], tumor size [14-16], histological and nuclear grades [17-20], histological subtype [21-23], ER status [24, 25], Her-2/neu expression [26, 27] and peritumoral vascular invasion [28-31]. This evidence concerns the gene ESR1 and breast cancer.