Breast cancer is commonly categorized into several subtypes: Luminal A (ER-positive with low histological grade), Luminal B (ER-positive with high histological grade), HER2-enriched, Claudin-low, basal-like (BL1 and BL2), immunomodulatory (IM), mesenchymal (M), mesenchymal stem-like (MSL), and normal breast-like tumors [10]. The gene discussed is ERBB2; the disease is breast cancer.