ALK and anaplastic large cell lymphoma: Based on their results, the most common subtype of mature T-cell lymphomas is PTCL, non-otherwise specified (PTCL, NOS; 26%), followed by angioimmunoblastic T-cell lymphoma (AITL; 18.5%), anaplastic large cell lymphoma, ALK-positive (ALCL, ALK+; 7%), and anaplastic large cell lymphoma, ALK-negative (ALCL, ALK−; 6%).