ESR1 and triple-negative breast carcinoma: Triple-negative breast cancer (TNBC) is characterized by a tumor subtype void of hormone receptors, such as the estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor 2 (HER2) (Zhou et al., 2018); thus, this tumor is associated with poor prognosis (Den Brok et al., 2017).