COMPARISON BETWEEN INTERPHASE AND METAPHASE CYTOGENETICS IN DETECTINGCHROMOSOME-7 DEFECTS IN HEMATOLOGICAL NEOPLASIAS

Monosomy 7 (-7) is one of the most common chromosomal abnormalities fo und in the leukemic cells of patients with acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS). Because patients with -7 hav e a poor prognosis, their identification is important for treatment pl anning. Conventionally, -7 is detected by the G-banding technique. Thi s study examines the use of fluorescent in situ hybridization (FISH) m ethodology to detect -7 cells in interphase nuclei and metaphase chrom osomes. Fifteen AML or MDS patients whose leukemic cells were found to have -7 by G-banding at disease presentation were studied. In 13 of t hese patients, -7 could be detected in interphase by FISH using a chro mosome 7-specific centromeric DNA probe. The two patients whose leukem ic cells were not detectable by interphase FISH had 7 and t(1q;7p), wh ich were detectable by FISH in metaphase using a chromosome 7-specific painting probe. Metaphase FISH was particularly useful in further def ining chromosome 7 defects in cells that contained aberrant or marker chromosomes. For example, in 6 patients, chromosome 7 sequences were d etectable in aberrant or marker chromosomes by metaphase FISH, but not by G-banding. These results suggest that metaphase FISH is an importa nt adjunct to conventional cytogenetic methods for defining chromosome 7 abnormalities in AML and MDS patients. Furthermore, interphase FISH is useful for follow-up studies in patients who are found informative for the FISH study at presentation.