ESR1 and breast cancer: A multicenter, retrospective analysis of 219 breast cancer patients with brain metastases recently published by the American researchers showed that the inconsistency rates of ER, PR, and HER-2 between the primary lesions and brain metastatic lesions were 16.7% (36/216), 25.2% (53/210), and 10.4% (21/201), respectively, of which 36.3% (70/193) were inconsistent in the expression of anyone receptor (ER, PR, or HER-2), and the receptor conversion led to a subtype conversion of 22.8% (50/193) (23).