ESR1 and breast cancer: For example, the majority of ER+/luminal-like tumors that are positive for ER and/or progestrone receptor (PR) respond well to hormonal interventions, whereas Erb-B2+ tumors characterized by amplified ERBB2 oncogene and/or Her2 protein overexpression can be effectively controlled by using various anti-Her2 therapies.4 Therefore, breast cancer patients have greatly benefited from molecular classification that is used for individualized therapies and results in obvious improvements in disease-specific survival.5