ERBB2 and breast cancer: The discrepancy between these studies might be because the definition of HER2-low-positive BC was not identical, as two previously reported studies showed HER2-low-positive defined as (ICH 2+/FISH−), while a recent pooled analysis and our study defined HER2-low-positive as (IHC) 1+ or IHC2+/in situ hybridization negative.