PDCD1LG2 and neoplasm: ICIs target cell-surface ‘immune checkpoints’—immune inhibitory pathways that normally function to mediate self-tolerance but that can be exploited by tumour cells to evade the host immune response.1 Indeed, the best recognised mechanism of evasion of the immune system by tumour cells is their upregulation of the immunosuppressive cell-surface ligands programmed cell death ligand-1 (PD-L1) and PD-L2.