Our findings suggest that STAT5 plays a crucial role in ALCL oncogenesis and that inhibition of the PDGFRβ/STAT5 axis, but also of the NPM-ALK-STAT3 axis, both upstream via imatinib/ALK inhibitors and downstream with AC-4-130, is therapeutically relevant in ALK+ ALCL. Here, STAT5B is linked to anaplastic large cell lymphoma.