In HER2 + BC, high tsMHC-II (HR = 0.22, 95%CI = 0.08–0.61, p = 0.004, Fig. 2E), CD4 (HR = 0.41, 95%CI = 0.23–0.75, p = 0.006, Fig. 2E), and CD8 (HR = 0.53, 95%CI = 0.30–0.95, p = 0.040, Fig. S1E) were associated with better DFS. This evidence concerns the gene CD8A and breast cancer.