Near‐tetraploidy in childhood B‐cell precursor acute lymphoblastic leukemia is a highly specific feature of ETV6/RUNX1 ‐positive leukemic cases

Near‐tetraploidy (82–94 chromosomes) makes up fewer than 1% of childhood acute lymphoblastic leukemia (ALL) cases and has been reportedly associated with a possibly poorer prognosis compared with other ploidy groups. We analyzed 783 patients enrolled in the ALL‐BFM‐Austria 86, ‐90, ‐95, ‐99/2000 and Interfant‐Austria 99 trials in order to assess its incidence, biological characteristics, and prognostic relevance. Twelve of 783 patients (1.5%) had a near‐tetraploid ALL. Fluorescence in situ hybridization revealed that eight of the nine B‐cell precursor (BCP) cases and none of the three T‐cell ALL cases had an ETV6/RUNX1 rearrangement. After a median follow‐up of 11.4 years, none of the patients has relapsed or died. Thus, near‐tetraploidy appears to be a specific feature of ETV6/RUNX1 + BCP ALL cases that in turn may explain its excellent outcome. © 2006 Wiley‐Liss, Inc.