Tumor cells have the capacity to evade clearance by macrophages through the upregulation of antiphagocytic surface proteins including cluster of differentiation 47 (CD47), programed death-ligand 1 (PD-L1), programed cell death protein 1 (PD1), cytotoxic T-lymphocyte-associated protein 4 (CTLA4), and beta-2-microglobulin (B2M) (49–52). Here, PDCD1 is linked to neoplasm.