ESR1 and breast carcinoma: In such a way, breast carcinomas can be classified into five main molecular subtypes: luminal A (ER+/PR+/HER2− with low or intermediate differentiation), luminal B (ER+/PR−/HER2+ with high differentiation grade), basal-like (ER−/PR−/HER2−) also called triple-negative breast cancer (TNBC), HER2-enriched (ER−/PR−/HER2+), and normal breast-like (overexpressing genes of adipose and other nonepithelial cells) [4,5].