Cytogenetic and FISH techniques in myeloid malignancies.

Chromosome analysis is an essential part of the diagnostic testing of myeloid malignancies. Good chromosome preparations are essential for a complete cytogenetic analysis. This means plentiful metaphase spreads with well-spread crisply banded chromosomes. To achieve such a result, several variables, including the growth rate of the leukemic cells, are critical. The method described in this chapter has been extensively tested and should produce reasonable results from most cases. Fluorescence in situ hybridization (FISH) is less influenced by sample variation and as a result may be obtained from either metaphase spreads or interphase cells. Moreover, FISH is capable of describing chromosome rearrangements at the gene level, rather than at the gross level shown by conventional cytogenetics. It does not, however, provide information on genetic rearrangements other than at the specific target site of the probe used, unlike conventional cytogenetics. Thus, these two techniques complement each other and are both now essential elements of chromosome analysis.