Axillary nodal status is the most significant prognostic factor for predicting survival in patients with breast cancer even though many other factors such as tumor size, histological grade, S-phase fraction, DNA index, tumor ploidy, estrogen receptor and progesterone receptor status, and Her-2/neu and Ki-67 status have provided additional information to guide adjuvant therapy [11]. This evidence concerns the gene ESR1 and breast cancer.