PDCD1 and neoplasm: The POLE- and MSI-mutated subgroups harbor high neoantigen loads, increased immune checkpoint expression (such as programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1)), as well as increased numbers of tumor-infiltrating lymphocytes (TILs); these findings suggest that these molecular subgroups are good candidates for immunotherapy [13,14].