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. This evidence concerns the gene ERBB2 and breast cancer.