ERBB2 and breast cancer: Multivariate logistic regression model for factors affecting pathologic response among BC patients with over and equivocal HER2 protein expression revealed that HER2 IHC 3+ is an independent predictor of pCR over HER2 gene amplification level; (OR, 18.00; 95%CI, 89.07–2.66; P = 0.004).