In the field of targeted breast cancer therapy, several prognostic markers including clinical stage [1], histologic grade [2], estrogen receptor (ER)/progesterone receptor (PR) status [3-5], human epidermal growth factor receptor-2 (HER2) [6,7], and the Ki-67 proliferation index [8] have already been identified and validated. This evidence concerns the gene ESR1 and breast carcinoma.