In a series of studies over recent years, Manso et al. (2021) evaluated PD-1 expression in 168 PTCL subtypes via immunohistochemistry using a cutoff value of 10% and reported that PD-1 was expressed in 61.6% (52/86) of AITL, 39.3% (22/56) of PTCL-NOS, and 13.3% (2/15) of ALK− ALCL cases. This evidence concerns the gene ALK and mature T-cell and NK-cell non-Hodgkin lymphoma.