found that mono- and biallelic deletions of PDCD1, which encodes PD-1, are recurrently observed in human T-cell lymphomas with frequencies of up to 30%, indicating high clinical relevance; these findings imply that PD-1 is a potent haploinsufficient tumor suppressor in T-cell lymphomas (18). This evidence concerns the gene PDCD1 and T-cell non-Hodgkin lymphoma.