PDCD1 and neoplasm: A number of hematologic malignancies, including HL and diffuse large-B cell lymphoma (DLBCL), express the PD-1 ligands, PD-L1 and PD-L2, presumably as a means of dysregulating the immune response through PD-1:PD-L1/L2 interactions between tumor cells and T lymphocytes leading to T-cell exhaustion [3–5].