Similarly, for ER-positive and HER2-negative BC, we observed higher mastectomy rates in older patients (39.4%, 23.7%, and 15.6% for patients aged >80 years, 75–80 years, and 70–74 years, respectively), and in younger patients (35.3% and 24.8% for patients aged ≤40 years and 41–50 years, respectively), with significant differences in multivariate analysis (Table 3). This evidence concerns the gene ERBB2 and breast cancer.