ERBB2 and breast cancer: The comparison between the HER2 categories showed the following features: ypT0, ypT1a and ypT1b were found in 93.7%, 69.2% and 76.9% of HER2 IHC 3+ BC vs. 6.3%, 30.8% and 23.1% of HER2 IHC 2+/SISH+ BC, respectively (P = 0.003).