Detecting hypodiploidy with endoreduplication and masked hypodiploidy in B‐cell acute lymphoblastic leukemia using multicolor flow cytometry

Abstract

Background: Multicolor flow cytometry-based DNA-ploidy (MFC-ploidy) analysis is a simple, sensitive, and popular method for ploidy analysis in B-cell acute lymphoblastic leukemia (B-ALL). However, the utility of MFC-ploidy in the detection of B-ALL with endoreduplication or masked hypodiploidy has not been reported. Herein, we studied the patterns of MFC-ploidy assessment and its utility to detect B-ALL with hypodiploidy and endoreduplication.Methods: MFC-ploidy analysis was performed using FxCycle Violet-dye-based method, and cytogenetic ploidy was evaluated using chromosomal-counting and FISH analysis. A total of 20 B-ALL cases with endoreduplication were studied for the patterns of MFC-ploidy analysis and compared with 250 patients with hyperdiploidy and 11 cases with pure hypodiploidy.Results: All B-ALL with endoreduplication revealed two distinct peaks (populations) on MFC-ploidy analysis: the first (hypodiploid) peak (median-DNA-index [DI], 0.82; range, 0.6-0.95) and the second (hyperdiploid) peak with almost twice DI (median-DI, 1.53; range, 1.14-1.75). Cytogenetic findings were available in 19 cases and confirmed hypodiploidy with endoreduplication in 13/19 (68.4%) and only hypodiploidy in 3/19 cases. The remaining three cases showed hyperdiploid blasts in cytogenetic studies. Of these three, two cases had <10% blasts population with hypodiploidy. Thus, masked-hypodiploidy could be diagnosed correctly in 3/19 cases on MFCploidy analysis.Conclusion: MFC-ploidy analysis shows a characteristic pattern of DNA-ploidy in samples with endoreduplication. It allows the distinction between samples with masked hypodiploidy from true hyperdiploidy. An integrated approach involving cytogenetic and MFC-ploidy detection is very helpful in the risk stratification of B-ALL in routine clinical practice.

Transcriptomic Analysis of Conserved Telomere Maintenance Component 1 (CTC1) and Its Association with Leukemia

“…The cytogenetic data of ALL cases showed chromosomal translocations t(9;15)(p13;q11.2), t(1;19)(q25;p13.3), t(9;22)(q34;q11.2), and hyperdiploidy with other abnormalities in B-cell ALL while hypodiploidy was noted in T-cell ALL cases. Several studies have identified the same chromosomal translocations and the presence of hypo and hyperdiploid chromosomes in ALL cases [ 35 , 36 , 37 , 38 , 39 ].…”

Hyperdiploidy: the longest known, most prevalent, and most enigmatic form of acute lymphoblastic leukemia in children

“…Several of these technologies are quite sophisticated, so it is quite surprising that those being used almost exclusively for treatment stratification today are still the rather basic options that have been already in use for many decades. The reason for this is that these diagnostic tools are simple to perform, cheap, and fast [109][110][111][112]. However, the fact that they are still considered sufficient also implies that, for clinical purposes, a more in-depth evaluation of the intricate features of such cases is deemed completely unnecessary, since these patients have in any case an overall very good outlook (Table 3).…”

Issue Highlights—May 2022

“…DNA‐ploidy is an established prognostic factor in B‐cell acute lymphoblastic leukemia, being hypodiploidy (<43 chromosomes, DNA Index <0.95) associated with a dismal outcome, and hyperdiploidy (>50 chromosomes, DNA Index >1.16) conversely considered a good prognostic indicator. In rare occasions the irregular mitoses of truly hypodiploid cells may generate false hyperdiploid populations, due to the phenomenon known as endoreduplication and masked hypodiploidy (Chaturvedi et al, 2022). This rare but clinically important phenomenon has been elegantly described here by coupling DNA‐ploidy analysis and multicolor surface staining, thus demonstrating the occurrence of the chromosome defect just within the abnormal blast population.…”