Effects of platelets on immune cell trafficking in breast cancer. (A) Infiltration by neutrophils, cMOs, B cells, CD8⁺ T cells, CD4⁺ T cells, and (B) CD4⁺ T-cell subsets as assessed by flow cytometry, as well as (C) size and weight of orthotopic 4T1 tumors in mice receiving platelet depleting or isotype control antibodies; quantitative data are shown (mean ± SEM for n = 4-6 mice per group; ∗P < .05/∗∗P < .01/∗∗∗P < .001 vs isotype control; ns, not significant). (D) Correlation between the ratio of extravascular MPO⁺ neutrophils and CD8⁺ T cells (NLR, neutrophil/lymphocyte ratio) and intravascularly accumulated integrin β3⁺ platelets, as assessed by immunohistochemical analyses of human TNBC samples; representative images and quantitative data are shown. (E) Recurrence-free survival of patients with breast cancer from the METABRIC breast cancer cohort exhibiting ITGA2B^low and ITGA2B^high expression levels (z-value ≥1.5 served as the cutoff).