Breast cancer molecular subtypes: Luminal A: ER+ and/or PR+ (PR ≥ 20%), HER2-, Ki-67 < 14%; Luminal B (HER2-): ER+ and/or PR+ (PR < 20%), HER2-, Ki-67 ≥ 14%; Luminal B (HER2+): ER+ and/or PR+, HER2+, Ki-67 any; HER2-enriched: ER−, PR−, HER2+; triple-negative breast cancer (TNBC): ER−, PR−, HER2-; BRCA: breast cancer gene; HT: hormone therapy; CHT: chemotherapy, TNM: tumor, node, and metastasis; HER2: human epidermal growth factor receptor 2. This evidence concerns the gene ERBB2 and breast cancer.