Within this rather rare disease group, the most common subtype is PTCL-not otherwise specified (NOS), which summarizes cases not attributable to other entities, followed by angioimmunoblastic T-cell lymphoma (AITL), ALK+ anaplastic large cell lymphoma (ALCL), and ALK− ALCL [46,48,49]. This evidence concerns the gene ALK and mature T-cell and NK-cell non-Hodgkin lymphoma.