ERBB2 and breast cancer: HER2 plays a pivotal role in the pathogenesis of BC and other malignancies, with its expression or gene amplification frequently correlated with aggressive disease phenotypes and poor clinical outcomes.4 Consequently, HER2-positive is used to describe tumor cells exhibiting HER2 protein expression or HER2 gene amplification, defined as immunohistochemistry (IHC)3+ or IHC2+ with fluorescence in situ hybridization (FISH) positivity.5 Importantly, the elevated expression of HER2 on the surface of tumor cells presents a therapeutic target for the development of specific anti-HER2 agents.