Interphase FISH excluded JAK2 translocations in 217 PTCLs from 200 patients with: angioimmunoblastic TCL: 60; ALCL, 53 (15 ALK-positive, 23 ALK-negative, and 15 cutaneous); PTCL-not otherwise specified, 59; extranodal NK/TCL, 11; mycosis fungoides, 5; and other cytotoxic PTCLs. The gene discussed is ALK; the disease is mature T-cell and NK-cell non-Hodgkin lymphoma.