Current factors contributing to the development of BC in obese women include increased levels of sex steroid hormones such as estrogen, insulin resistance, increased levels of insulin-like growth factors (IGFs), oxidative stress, adipocytokines such as adiponectin, leptin and visfatin (Berger, 2014[3]; Engin, 2017[13]), and ligand-independent activation of ERα (Catalano et al., 2004[8]). Here, ESR1 is linked to breast cancer.