Also, the BCSS difference was statistically significant between HER2-positive and HER2-negative subgroups in ER-positive/PR-positive, ER-positive/PR-negative, and ER-negative/PR-negative breast cancers (Figures 4A, B, D), except for the ER-negative/PR-positive subtype (Figure 4C). This evidence concerns the gene PGR and breast cancer.