The AMBER Consortium [5] presented results separately for premenopausal and postmenopausal women, reporting that, among premenopausal women, BMI at age 18 years was inversely associated with risk of ER+ breast cancer but not with risk of ER– breast cancer or TNBC (≥ 30 vs. 20–24.9 kg/m2, ER+ OR = 0.65, 95% CI = 0.42–1.01; ER– OR = 1.00, 95% CI = 0.63–1.58; TNBC OR = 1.08, 95% CI = 0.59–1.98). This evidence concerns the gene ESR1 and breast cancer.