ESR1 and triple-negative breast carcinoma: Luminal A tumors (ER+/PR+/HER2−) and Luminal B tumors (ER+/PR+/HER2+) are hormone-receptor positive, while HER2-enriched tumors (ER−/PR−/HER2+) and basal-like or triple-negative breast cancers (TNBC; ER−/PR−/HER2−) represent more aggressive subtypes.