ERBB2 and breast carcinoma: Breast cancer is the most common malignant tumor among women worldwide and one of the leading causes of cancer‐related deaths.[1] Human epidermal growth factor receptor 2 (HER2) plays a critical role in the molecular subtyping and treatment of breast cancer, with its expression status directly affecting patient prognosis and therapeutic strategies.[2] With the emergence of novel antibody‐drug conjugates (ADCs), the subtype of HER2‐low expression (immunohistochemistry [IHC] 1+ or IHC 2+ with in situ hybridization [ISH] ‐) has gradually gained attention.