ALK and mature T-cell and NK-cell non-Hodgkin lymphoma: Peripheral T‐cell lymphomas (PTCLs) comprise more than 30 distinct histologic subtypes including anaplastic lymphoma kinase (ALK)‐positive anaplastic large cell lymphoma (ALCL) and ALK‐negative ALCL, extranodal natural killer (NK)/T‐cell lymphoma (ENKTL), angioimmunoblastic T‐cell lymphoma(AITL), and PTCL, not otherwise specified (PTCL‐NOS) according to World Health Organization (WHO) classification system 2017.4