Yang CF, et al. - The purpose of this work was to distinguish between aggressive NK-cell leukaemia (ANKCL) and extranodal NK/T-cell lymphoma (ENKTCL) with secondary bone marrow involvement. Those with no extramedullary mass exhibited a prominent association with chromosome 7 abnormalities. Chromosome 6q deletion, commonly reported in ENKTCL, was noted in 2 patients with extramedullary mass. It was not found in patients with no extramedullary mass.Since ANKCL with no extramedullary mass exhibited distinct outcome and genetic features, it ought to be distinguished from ENKTCL with bone marrow involvement.