To study the transcriptional profile of BC-associated senescent CD4+ T cells, we performed a microarray assay of peripheral blood cell subsets sorted as KLRG-1+CD57+ EM/EMRA CD4+ cells (DPBC) and KLRG-1−CD57− EM/EMRA CD4+ cells (DNBCs) from treatment-free BC patients and KLRG-1+CD57+ EM/EMRA CD4+ cells from HDs (DPHD). This evidence concerns the gene KLRG1 and breast cancer.