In this study, 107 children with acute lymphoblastic leukemia (ALL) were analysed for the presence of hyperdiploidy by cytogenetics and interphase fluorescence in situ hybridisation (I-FISH). Structural aberrations in hyperdiploid cells were investigated by multiple colour FISH (mFISH).
Clones with high hyperdiploidy (>50 chromosomes) (HeH) were found in 46 patients (43%). In nine of these (20%), the abnormal clone was present in 20% of cells.
Structural rearrangements in the HeH clone were found in 10 patients (22%). In this study, HeH karyotypes containing structural aberrations were an indication of a poor prognosis in childhood ALL.