A strategy to detect chromosomal abnormalities in children with acute lymphoblastic leukemia.

Conventional cytogenetics (CC) can be used to identify chromosomal abnormalities that are predictors of treatment outcome in acute lymphoblastic leukemia (ALL). The detection of abnormalities in ALL is difficult because low mitotic index and poor-quality metaphases are obtained. Flow cytometry (FC) and fluorescence in situ hybridization (FISH) can be used to detect aneuploidy in any phase of the cell cycle, increasing the number of analyzable cells. The aim of this study was to develop a strategy combining these methods to improve the frequency of chromosome abnormality detection. One hundred children with newly diagnosed ALL were included. CC and DNA content analysis by FC were performed in all patients. The numerical abnormalities identified by both methods were compared and patients were classified as concordant or discordant. FISH was used to support aneuploidy results in discrepant cases using centromeric probes for the chromosomes most frequently involved in aneuploidy. CC and FC showed high concordance (86%). Fourteen cases were discrepant: nine showed hypodiploidy and low hyperdiploidy by cytogenetics and five showed high hyperdiploidy by FC. FISH confirmed aneuploidy in 12 cases in which it could be performed. High hyperdiploidy was the most common abnormality; the 31 cases showing this aneuploidy were identified by FC. The search for abnormalities must begin by measuring DNA content to detect this aneuploidy, which is useful to evaluate the patient's risk. However, it is important to screen for structural abnormalities by CC or molecular techniques. This strategy may detect chromosomal abnormalities, optimizing resources in laboratories where not all the screening methods are available.