TNBC, which is identified by the lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), is the most aggressive subtype of breast cancer (Guerneri et al., 2013; Zaharia et al., 2013; Schmadeka et al., 2014). The gene discussed is ESR1; the disease is breast cancer.