Tumour responses to anti-PD-1/PD-L1 immunotherapy are mediated by T cells that had been previously blocked by the PD-1−PD-L1 interaction.40–42 Thus, it is reasonable to assume that pre-existing tumour-infiltrating lymphocytes and PD-L1 expression might correlate with clinical response to anti-PD-1/PD-L1 immunotherapy. This evidence concerns the gene PDCD1 and neoplasm.