ESR1 and breast cancer: The study examined associations between SMR and breast density, mode of detection, age, tumor size, estrogen receptor status, progesterone receptor status, human epidermal growth factor receptor 2 status, Ki67, histological grade, axillary lymph node involvement (ALNI), histological type, and breast cancer-specific survival, utilizing the Chi-squared test, ANOVA, Fisher's exact test, Kaplan-Meier curves, and Cox regression.<h4>Results</h4>The mean age was 68 years (range 55-91).