ESR1 and neoplasm: Endocrine therapies targeting the estrogen receptor (ER) using aromatase inhibitors, such as letrozole, preventing ER signaling (Finn et al., 2015; Finn et al., 2016b; Goetz et al., 2017), selective ER degraders, like fulvestrant (Turner et al., 2015; Sledge et al., 2017; Turner et al., 2018), or selective ER modulators as tamoxifen (Tripathy et al., 2018b) substantially reduced tumor recurrence and improved overall survival (OS) (Abe et al., 2005).