ALK and mature T-cell and NK-cell non-Hodgkin lymphoma: Peripheral T-cell lymphomas (PTCLs) are a heterogeneous group of non-Hodgkin lymphomas including PTCL-not otherwise specified (PTCL-NOS), angioimmunoblastic T-cell lymphoma (AITL), and anaplastic lymphoma kinase (ALK)-positive or -negative anaplastic large-cell lymphoma (ALCL) (1, 2).