Based on the molecular subtype, four different types of breast cancer have been identified: (1) Luminal A (HR+/HER2−) (71%), (2) luminal B (HR+/HER2+) (12%), (3) HER2-enriched (HR-/HER2+) (5%), and (4) triple-negative (HR−/HER2−) (12%) [1]. The gene discussed is ERBB2; the disease is breast cancer.