ESR1 and breast cancer: The chromosome 6q.21 region includes several genes involved in sex-steroid hormonal signaling, such as SYNE1, ESR1 and CCDC170, with multiple SNVs previously associated with female hormone-dependent diseases including endometrial cancer (rs79575945, rs2046210 and rs9340799) [18,20,21], breast cancer (rs2046210, rs9383590 and others) [22,23], infertility (rs9340799) [24] and recurrent implantation failure (rs9340799) [25].