By analysis of a tissue microarray from the Breast Tumor Bank with samples from 180 patients with breast cancer for whom clinical data are available, we found that patients with high levels of platelets and low levels of CD8+ T cells had decreased metastasis-free survival than those with the low levels of platelets and high CD8+ T cells (HR = 2.84 (1.14–7.08) log-rank P = 0.02, Fig. 5g). Here, CD8A is linked to breast cancer.