Based on the expression of hormone receptors and amplification of the human epidermal growth factor receptor 2 (Her2), breast cancer is divided into four molecular subtypes: Luminal A (ER+/PR+/HER2−), Luminal B (ER+/PR+/−/HER2+, or ER+/PR+/HER2− with KI67 ≥ 14%), HER2-enriched (ER−/PR−/HER2+), and triple-negative breast cancer (ER−/PR−/HER2−, TNBC) [2]. Here, ERBB2 is linked to breast cancer.