ERBB2 and breast cancer: Additionally, BC can be classified according to PAM50 gene signature into five intrinsic molecular subtypes: Luminal A (LumA; ER+/PR+/HER2–/ki67 > 14%), Luminal B (LumB; ER+/PR–/+HER2–/ki67 > 14%), HER2-enriched, basal-like, and normal-like, with each molecular subtype exhibiting distinct features and prognosis [3, 4].