ESR1 and breast cancer: Stratified analysis by menopausal status demonstrates that a significantly increased risk of breast cancer was confined to the pre-menopausal women (indicating a higher female sex hormone level and younger age) who had mother impacted by breast cancer (OR = 5.39, 95% CI: 1.13–25.61), and this association was enhanced for women with the ER+ tumor type (OR = 8.67, 95%CI: 1.78–42.25).