ERBB2 and breast cancer: The molecular classification of BC was based on the PAM50 signature, with clustering in the following groups: Luminal A (ER+ and/or PR+, HER2−, and Ki-67+ <20%), Luminal B (ER+ and/or PR+, HER2−, and Ki-67+ ≥20%), Luminal B-HER2+ (ER+ and/or PR+ and HER2+), HER2+ (ER-, PR-, and HER2+), HER2-enriched (ER+, PR+, and HER2+), and triple-negative (ER-, PR-, and HER2-).