To analyze the possible implication of DDX21 in rRNA biogenesis and cell metabolism of ALK+ ALCL, we investigated whether processing of pre-rRNA was interrupted by silencing DDX21. Autoradiography of RNA purified from ALK+ ALCL cells with strong DDX21 knockdown demonstrated a clear delay in processing of 32S-labeled pre-rRNA. This evidence concerns the gene DDX21 and anaplastic large cell lymphoma.