ESR1 and breast carcinoma: Treatments that target tumor responses to estrogen, including selective estrogen receptor modulators (e.g., tamoxifen), agents blocking estrogen biosynthesis (e.g., aromatase inhibitors), and estrogen receptor antagonists (e.g., fulvestrant) are an important adjuvant to first line surgery, chemotherapy or radiation for women with ER+ve breast cancers (Pagani et al., 2010; Liu et al., 2017).