ESR1 and breast cancer: This public dataset contains not only the gene expression data of the patients’ samples, but also relevant information about each patient, recorded in metadata [30]: lymph node status, estrogen receptors status, progesterone receptor status, human epidermal growth factor receptor 2 (HER2) status, histological grade, size in millimetres, adjuvant treatment, chemotherapy, recurrence or death from breast cancer, distant metastasis or death from breast cancer, and death from breast cancer.