Amplification or overexpression of the human epidermal growth factor receptor 2 (HER2) is observed in approximately 20% of breast cancers (BCs) and is often associated with an aggressive clinical behavior and poor outcomes.1 When overexpressed, the HER2 oncogene is the dominant driver of BC biology, and treatment strategies targeting HER2 have become the standard of care in all the disease settings since 2006.2 Currently, four anti‐HER2 agents are licensed in Europe: trastuzumab, lapatinib, pertuzumab and T‐DM1. This evidence concerns the gene ERBB2 and breast cancer.