It is estimated that roughly 20% of all diagnosed breast cancer cases will display the triple-negative (TN) phenotype [2,3], characterized by the lack of expression of estrogen (ER) and progesterone (PR) receptors and lack of expression and/or gene amplification of human epidermal growth factor receptor 2 (EGFR2/HER2) [2,3]. The gene discussed is ESR1; the disease is breast cancer.