PGR mRNA expression was significantly associated with improved prognosis in ER+ breast cancer (adjusted P-Value = 0.0003); however, in our genome-wide analysis, we identified hundreds of genes with stronger prognostic association in ER+ breast cancer (PGR's association was ranked 728th out of the approximately 13 K genes (approximately 6th percentile), Figure 5, Additional file 1: Table S2). This evidence concerns the gene PGR and breast cancer.