Comparison between interphase and metaphase cytogenetics in detecting chromosome 7 defects in hematological neoplasias

Abstract

Monosomy 7 (–7) is one of the most common chromosomal abnormalities found in the leukemic cells of patients with acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS). Because patients with –7 have a poor prognosis, their identification is important for treatment planning. Conventionally, –7 is detected by the G‐banding technique. This study examines the use of fluorescent in situ hybridization (FISH) methodology to detect –7 cells in interphase nuclei and metaphase chromosomes. Fifteen AML or MDS patients whose leukemic cells were found to have –7 by G‐banding at disease presentation were studied. In 13 of these patients, –7 could be detected in interphase by FISH using a chromosome 7‐specific centromeric DNA probe. The two patients whose leukemic cells were not detectable by interphase FISH had –7 and t(1q;7p), which were detectable by FISH in metaphase using a chromosome 7‐specific painting probe. Metaphase FISH was particularly useful in further defining chromosome 7 defects in cells that contained aberrant or marker chromosomes. For example, in 6 patients, chromosome 7 sequences were detectable in aberrant or marker chromosomes by metaphase FISH, but not by G‐banding. These results suggest that metaphase FISH is an important 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.