Value of fluorescence in situ hybridization in detecting retinoic acid receptor alpha rearrangement for the diagnosis of acute promyelocytic leukemia

Objective To study the value of fluorescence in situ hybridization (FISH) in detecting retinoic acid receptor alpha (RARα) rearrangement for the diagnosis of acute promyelocytic leukemia (APL). Methods A dual color break apart rearrangement probe for RARα gene and a dual color translocation probe for promyelocytic leukemia (PML)/RARα fusion gene were used to perform FISH in 4 patients with typical morphological changes of APL but lacking both t(15;17) and PML/RARα fusion transcript through karyotypic analysis and RT-PCR assay. Results Of the 4 patients, two had negative results, one showed a fusion signal indicating PML/RARα fusion gene in 80% of interphase cells, and the other one had no PML/RARα fusion gene but showed a duplication and rearrangement of RARα gene. Conclusions It is possible to detect RARα rearrangement by FISH which could not be found by karyotypic analysis or RT-PCR assay among a part of APL patients. Thus, it is helpful for the diagnosis of APL.