ESR1 and breast cancer: Among the four datasets (METABRIC, TCGA, GSE40267, GSE19783) provided, the METABRIC dataset has long follow-up (median: 94 months), average characteristics (78% Estrogen receptor (ER) positive, 12% human epidermal growth factor receptor 2(HER2) positive), and the largest number of breast cancer patients (1262 patients).