According to hormonal receptor status, BMI ≥25.8 kg/m2 was associated with breast cancer-specific death (HR = 4.95; 95% CI: 1.05–23.35) and BMI <21.2 kg/m2 was associated with all-cause (HR = 2.91; 95% CI: 1.09–7.77) and breast cancer-specific death (HR = 7.23; 95% CI: 1.57–33.34) among patients with ER + or PgR + tumors. Here, ESR1 is linked to breast cancer.