PDCD1 and neoplasm: Immune checkpoint inhibitors include anti-cytotoxic T lymphocyte antigen 4(CTLA-4), anti-programmed cell death 1(PD-1), and anti-programmed cell death ligand 1 (PD-L1) antibodies, which are monoclonal antibodies that block the inhibition of T cell function and enhance the cytotoxic activity of T cells, thereby improving anti-tumor immunity and being widely used in tumor immunotherapy (1, 2).