Subsequently, recurrent constitutive activation of ALK through gene rearrangements or gain-of-function mutations has been documented in numerous cancer types including non–small cell lung cancer, inflammatory myofibroblastic tumor, anaplastic large cell lymphoma, diffuse large B-cell lymphoma, neuroblastoma, breast, colorectal, and renal cell carcinomas (2–5). The gene discussed is ALK; the disease is anaplastic large cell lymphoma.