Spectral karyotyping study of chromosome abnormalities in human leukemia

Chromosomal analysis plays an important role in the diagnosis, treatment and prognosis of human leukemia. Currently, the GTG-banding technique (G-banding) is the most commonly used diagnostic method in clinical cytogenetics. G-banding analysis of subtle chromosomal rearrangements or complex karyotypes with multiple markers can be inadequate because of poor chromosome morphology and/or an insufficient yield of analyzable metaphases. Fluorescence in situ hybridization (FISH) is a highly sensitive and specific method to detect chromosomal alterations. Conventional FISH is used optimally in instances where only one or a few abnormalities are investigated. Spectral karyotyping (SKY), a novel cytogenetic technique, has been developed to unambiguously display and identify all chromosomes at one time using a spectrum of 24 different colors. This report presents the use of SKY for examination of the entire karyotype in specimens with complex chromosomal abnormalities from three leukemia patients. Conventional cytogenetic analysis (G-banding) showed complex hyperdiploid clones with multiple markers in each case. SKY was able to clarify and identify additional cryptic chromosomal translocations [e.g., t(2;10), t(3;10), t(5;7), t(7;18), t(9;17), t(10;12), t(13;16)] insertions [e.g., ins(17;9), ins(20;Y)], duplications [e.g., i(8)(q10), dup(4)(q31q35)] and marker chromosomes in each case. This study demonstrates that the combination of SKY and G-band techniques results in a more complete characterization of the complex chromosomal aberrations seen in leukemia.