Luminal B BC is characterized by the variable expression and absence of specific receptors in various combinations (ER+/−, PR+/−, HER2−/+), along with the expression of particular genes (ESR1, GATA3, KRT8, KRT18, XBP1, FOXA1, TFF3, SQLE, LAPTM4B). Here, ESR1 is linked to breast cancer.