ERBB2 and breast cancer: The low expression of HER2 was 71.45% and 6.59% in the HR-positive/HER2-negative cohort and triple-negative cohort of primary breast cancer, respectively (p<0.01), and the residual breast cancer HR-positive/HER2-negative cohort and triple-negative cohort after neoadjuvant therapy were 66.72% and 5.75% respectively (p <0.01).