ALK and mature T-cell and NK-cell non-Hodgkin lymphoma: The majority of cases fall under angioimmunoblastic T‐cell lymphoma (AITL), anaplastic large cell lymphoma (ALCL; ALK+ or ALK‐ forms), and PTCL‐not otherwise specified (PTCL‐NOS), the latter forming a catch‐all group of unclassifiable PTCL.