ALK and mature T-cell and NK-cell non-Hodgkin lymphoma: In North America, the most common PTCL subtypes are peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) (34%); angioimmunoblastic T-cell lymphoma (AITL) (16%); anaplastic lymphoma kinase (ALK)-negative anaplastic large-cell lymphoma (ALCL) (16%); and ALK-positive ALCL (8%).