Although the present study and those of other authors (4–7) demonstrate a clear clinical benefit of PD-1 blockade in T-cell malignancies, it is important to underline that PD-1 is a potent haplo-insufficient tumor suppressor in T-cell lymphoma (8), and that its inhibition might potentially promote lymphomagenesis or accelerate neoplastic T cell growth. This evidence concerns the gene PDCD1 and T-cell non-Hodgkin lymphoma.