Differentially methylated regions in the buffy coat samples include regions associated with surfeit locus protein 6 (SURF6), deregulation of which have been reported in the peripheral blood cells of breast cancer patients [38]; ESRRB, a key regulator of stem cell pluripotency [30] and self-renewal [39, 40]; and FBXO38, which mediates the ubiquitination and degradation of the substrate programmed cell death protein 1 (PD-1) [41]. This evidence concerns the gene PDCD1 and breast cancer.