Abstract
Acute promyelocytic leukemia (APL) is generally characterized by t(15;17)(q24;q21). In some cases, the classic translocation cannot be identified by conventional methods, since the PML-RARA fusion protein results from complex, variant, or cryptic translocation. The diagnostic algorithm of APL starts with screening methods, such as flow cytometry (FC), followed by fluorescence in situ hybridization or polymerase chain reaction to confirm the diagnosis. Our aim was to develop a novel protocol for analyzing APL samples based on multidimensional dot-plots that can provide comprehensive information about several markers at the same time. The protocol included four optimized multidimensional dot-plots, which were tested by retrospective reanalysis of FC results in APL (n = 8) and non-APL (n = 12) acute myeloid leukemia (AML) cases. After predicting the potential position of hypergranular- and microgranular-type aberrant promyelocytes, the percentages of blast populations were examined within the gates in all AML cases. The percentage of blasts in each predefined gate was well above the cut-off value (95%) in APL cases in all tubes. In non-APL AML cases, the percentage of blasts in the same gates never reached the cut-off value in all investigated tubes, and even when it did in a single tube, the pattern was markedly different from that observed in APL cases. In conclusion, multidimensional dot-plots can be used for screening APL even in cryptic APL cases, although reproducibility across several laboratories would require standardization of antibodies and fluorochromes. This easy-to-use and quick method can support the diagnosis of APL and the prompt initiation of the appropriate treatment.
Highlights
IntroductionThe diagnostic algorithm of Acute promyelocytic leukemia (APL) starts with morphology and immunophenotype examinations [2]
Genetic alterations determine the biological behavior of acute myeloid leukemia (AML); these are the most effective independent prognostic factors and serve as the basis of Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Ann Hematol (2019) 98:1413–1420 at the time of diagnosis, are the major causes of early death [6,7,8]
As for the microgranular-type Acute promyelocytic leukemia (APL) cases, the position of the blast population differed from what we found in the hypergranular-type APL cases; dedicated gates were set up to predict the position of microgranular blasts (Fig. 2)
Summary
The diagnostic algorithm of APL starts with morphology and immunophenotype examinations [2]. Classic APL is characterized by a distinct morphology; yet, the microgranular type can mimic acute monoblastic leukemia, where the clinical history resembles APL regarding coagulopathy [1, 14]. The morphology and immunophenotype examination serve as screening, and the detection of t(15;17) confirms the diagnosis. In rare cases of APL that do not harbor the classic cytogenetically visible translocation but still possess the PML-RARA rearrangement, the polymerase chain reaction (PCR) is crucial for detecting the fusion gene [4, 5, 15, 16]
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