ALK and mature T-cell and NK-cell non-Hodgkin lymphoma: PTCL arises from mature post-thymic lymphocytes, and the most represented subtypes are PTCL not otherwise specified (PTCL-NOS), angioimmunoblastic T-cell lymphoma (AITL) and other nodal T-cell lymphomas of T-follicular helper origin (TFH), and anaplastic large cell lymphoma (ALCL) ALK-positive (ALCL-ALK+) and ALK-negative (ALCL-ALK-) (1).