CD4 and neoplasm: Definitive histological detection of these cells in tissue is challenging, and often their characterization omits CD25 for technical simplicity.51 52 Like effector CD4+ or CD8+ T cells, Tregs preferentially localize to stroma, rather than tumor foci in PDAC, but can be found in uninvolved and tumor compartments in equal proportion.9 53 However, the central location for the inhibitory action of these cells may be in peritumoral lymph nodes associated with PDAC.