Characterization of the lymphoid infiltrate in an unrelated series of locally advanced breast cancers disclosed a significantly higher prevalence of intratumor CD8+ T cells in HER2+ cases (median 1000, range: 730 to 1880) as compared with the HER2- subgroup (median 234, range: 117 to 890, P = 0.04). Here, CD8A is linked to breast cancer.