ALK and mature T-cell and NK-cell non-Hodgkin lymphoma: In T/natural killer (NK) cell neoplasia, PD-L1+ tumour cells were frequently found in anaplastic lymphoma kinase (ALK) + and ALK− systemic anaplastic large cell lymphoma (sALCL), occasionally in PTCL-NOS, and rarely in AITL [16–19].