ERBB2 and breast cancer: Breast cancer, a complex and heterogeneous disease, is grouped into four subtypes [Luminal A, Luminal B, Her‐2–enriched, and triple‐negative breast cancer (TNBC)] according to immunohistochemical markers, including estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 (Her‐2/neu), and cell proliferative index Ki‐67 [1].