Specifically, higher breast cancer PRSs were associated with lower regulatory T cells (Treg cells) [members of unassigned modules] (OR, 0.98; 95% CI, 0.97–0.9995; p = 0.0459) and lower CTLA-4 data [member of lymphocyte infiltration module] (0.76; 0.60–0.97; p = 0.0292) in advanced stages, and lower macrophage M2 (%) [member of unassigned module] (0.98; 0.96–0.99; 0.0038) and higher CD8+ T cells [members of T-cell/cytotoxic module] (1.002; 1.0003–1.004; p = 0.0221) in early stages. This evidence concerns the gene CD8A and breast cancer.