Furthermore, multivariate analysis revealed that the mutations remained as a significantly unfavorable factor for RFS (adjusted HR 6.52; 95% CI: 2.32–18.31; P < 0.001) and DRFS (adjusted HR 8.09; 95% CI: 2.83–23.18; P < 0.001) (Table 5) after adjustment for age, tumor grade, tumor size, lymph node metastasis, ER, PR, and adjuvant therapy in those breast cancer patients without HER2 expression. Here, ESR1 is linked to metastatic malignant neoplasm in the lymph nodes.