Breast cancer is categorized into four different molecular subtypes: Hormone receptor (HR)-positive (+)/Human epidermal growth factor receptor 2 (HER2)-negative (−) (Luminal A); HR+/HER2+ (Luminal B); HR−/HER2+ (HER2-enriched); and HR−/HER2− (triple negative). This evidence concerns the gene ERBB2 and breast carcinoma.