Activating mutations in JAK1 are found in CTCL, natural killer cell lymphoma (NKCL) and large granulocytic leukemia (LGL), as well as in 20% of ALK-negative anaplastic large cell lymphoma (ALCL), and treatment with ruxolitinib reduced tumor growth in an ALK-negative ALCL PDX model in vivo [133,134]. This evidence concerns the gene ALK and primary cutaneous T-cell non-Hodgkin lymphoma.