ERBB2 and breast cancer: Several reasons would potentially lead to the high proportion of HER2‐low in this study, including lack of ISH assay to reclassify BC with IHC 2+ as true HER2‐low BC or HER2‐positive BC, heterogeneity due to changes in testing HER2 protein expression with IHC between 2007 and 2021, and potential heterogeneity among different populations.