Breast cancer is classified into four major subgroups according to hormone receptors (HoR) and human epidermal growth factor receptor 2 (HER2) status, namely luminal‐A, luminal‐B, HER2‐enriched, and triple‐negative subtypes.13, 14 The heterogeneous of subgroups has substantial influence on survivals and recurrence risks of breast cancer. The gene discussed is ERBB2; the disease is breast cancer.