ERBB2 and breast cancer: In our study, the low ypN+ rate of 7.7% could be explained by routine axillary ultrasound combined with ultrasound-guided fine needle aspiration or core needle biopsy to confirm cN0 status; nearly 60% of patients had triple-negative or HER2-positive breast cancer and all populations had a high probability of achieving breast pCR of 40.5% regardless of biological subtype.