PDCD1 and neoplasm: Immune checkpoint inhibitors, essential components of immunotherapy, are antibodies targeting immune checkpoints like programmed cell death protein 1 (PD-1) and one of its ligands, programmed cell death 1 ligand 1 (PD-L1) on tumor cells and tumor infiltrating lymphocytes (TILs) to modulate T cell activity and suppress primary immune surveillance escape [4].