A case of acute myeloblastic leukemia with a novel variant of t(8;21)(q22;q22)

We encountered a case of acute myeloblastic leukemia (AML), with extramedullary leukemia (EML) and a masked type of the variant translocation t(8;21)(q22;q22). Morphologically, the AML M2 subtype according to the French-American-British (FAB) classification was present. Phenotypically, leukemic cells were negative for CD19 and positive for CD56. Clinically, the case showed chemo-refractoriness and a poor outcome. The initial karyotypic interpretation was t(8;9)(q22;q34) on G-banding. Multiplex-fluorescence in situ hybridization (multiplex-FISH) analysis revealed a three-way translocation involving chromosomes 8, 9, and 21, and identified a masked type of variant t(8;21)(q22;q22) translocation. The karyotype was finally determined as 45,X,-Y,der(8) t(8;21)(q22;q22), der(9)(8;9) (q22;q34), and der(21) t(9;21)(q34;q22). Results of FISH using the AML1/ETO probe and detection of the AML1/ETO fusion transcripts by reverse transcriptase-polymerase chain reaction (RT-PCR) support the karyotype as well as the sequence of the PCR product. Additionally, C-KIT mutation was detected.