ESR1 and breast cancer: Compared with other BC(Breast cancer) subtypes, TNBC(Triple negative breast cancer) has a worse prognosis and a higher early recurrence rate, typically with distant metastasis, owing to the absence of ER (Estrogen receptor),PR (Progesterone receptor) and Her-2(Human epidermal growth factor receptor 2) (Amorim et al., 2016; Volovat et al., 2020).