PDCD1 and neoplasm: Over the years, the rapid development of immune checkpoint blockade (ICB) therapies (e.g., inhibitors of cytotoxic T lymphocyte-associated protein 4 [CTLA-4] and programmed cell death-1/programmed cell death-ligand 1 [PD-1/PD-L1]) has revolutionized the clinical treatment landscape in a wide range of advanced tumor types.