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 typically display a poor chromosome morphology, was performed in order to investigate the pattern of numerical abnormalities, reveal the chromosomal origin of marker chromosomes, and identify translocations and other interchromosomal rearrangements not detected by G-banding analysis. In all cases the numerical changes could be fully characterized, and a non-random pattern of chromosomal gain was identified, with chromosomes X, 21, 14, 17, 6, 18, 4, and 10 being most frequently gained. The numerical changes had been partly misinterpreted in 12 of the 15 ALL patients using G-banding, and the present study 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 structural rearrangements, one of which was the prognostically important Philadelphia 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)(?;?), and t(9;21)(q12;q22)] have previously not been reported in ALL, emphasizing the value of SKY in identifying novel chromosomal rearrangements.