Identification of numerical and structural chromosome aberrations in 15 high hyperdiploid childhood acute lymphoblastic leukemias using spectral karyotyping

Spectral karyotyping (SKY) on metaphase spreads from 15 high hyperdiploid(> 51 chromosomes) childhood acute lymphoblastic leukemias (ALL), which typica lly display a poor chromosome morphology, was performed in order to investi gate the pattern of numerical abnormalities, reveal the chromosomal origin of marker chromosomes, and identify translocations and other interchromosom al rearrangements not detected by G-banding analysis. In all cases the nume rical changes could be fully characterized, and a non-random pattern of chr omosomal gain was identified, with chromosomes X, 21, 14, 17, 6, 18, 4, and 10 being most frequently gained. The numerical changes had been partly mis interpreted in 12 of the 15 ALL patients using G-banding, and the present s tudy hence emphasizes the importance of SKY in identifying such anomalies, some of which, i.e. + 4 and + 10, have been suggested to be prognostically important. The chromosomal origin of all marker chromosomes and of seven st ructural rearrangements, one of which was the prognostically important Phil adelphia chromosome, could be identified. Five rearrangements [der(1)t(1;14 )(q32;q21), der(2)t(2;8)(q36;?), der(3)t(2;3)(q21;?), der(8)t(8;14)(?;?), a nd t(9;21)(q12;q22)1 have previously not been reported in ALL, emphasizing the value of SKY in identifying novel chromosomal rearrangements.