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. The gene discussed is PGR; the disease is breast cancer.