ESR1 and breast cancer: The Women’s Health Initiative Cohort Study [26], which included only postmenopausal women, demonstrated that BMI at age 18 years was associated with a 17% reduced risk of ER+ breast cancer, but was not associated with TNBC (≥22.42 vs. < 19.33 kg/m2, ER+ OR = 0.83, 95% CI = 0.69–0.98; TNBC OR = 0.94, 95% CI = 0.56–1.56).