According to the expression of ER, PR and HER2, patients with BC were divided into four molecular subtypes: Basal (triple negative), Luminal A (LumA, ER/PR +, HER2 -), Luminal B (LumB, ER/PR +, HER2 +/-) and HER2 (ER/PR -, HER2 +). Here, ESR1 is linked to breast cancer.