Previous studies reported that loss of ER expression in the metastatic lesions was a negative prognostic factor for the survival of breast cancer patients (30–32), and a multicenter retrospective analysis of breast cancer patients with brain metastases showed that loss of ER expression in the brain metastatic lesions was associated with poor survival (P = 0.03), but the patients acquired ER expression simultaneously showed a survival advantage (23). The gene discussed is ESR1; the disease is breast cancer.