1,3,4,5,9 Department of Assisted Reproduction and Genetics, Jaslok Hospital and Research Centre, 15, Dr. G. Deshmukh Marg, Mumbai, Maharashtra 400026, India. 2Department of Hematology, Jaslok Hospital and Research Centre, 15, Dr. G. Deshmukh Marg, Mumbai, Maharashtra 400026, India and Department of Pathology, Bhatia Hospital, Mumbai, Maharashtra 400007, India. 6,7Department of Pathology, Bhatia Hospital, Mumbai, Maharashtra 400007, India. 8Department of Hematology, Jaslok Hospital and Researc
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Context: Variants of standard translocations in leukemia are occasionally suspected initially by fluorescence in-situ hybridization (FISH), due to a different signal pattern. In many cases, this is due to the involvement of an additional chromosome, eading to a complex three-way translocation. If the breakpoints are in the telomeric region, the cryptic translocation may not be visible on karyotyping. We describe here the characterization of a variant AML1/ ETO fusion involving 6q in a patient with AML-M2 Aims: To identify and confirm the extra chromosome involved in a variant AML1/ETO translocation in a case of AML-M2.
Settings and Design: First routine FISH for AML1/ ETO and conventional karyotyping was carried out. Reflex FISH was set up on previously Giemsabanded metaphases in two rounds to confirm that chromosome 6 was additionally involved in the AML1/ETO translocation.
Material and Methods: Heparinized bone marrow aspirate was obtained from a suspected case of AML-M2. Cytogenetic analysis by routine FISH for AML1/ETO and conventional karyotyping was carried out. Reflex FISH was set up on Giemsabanded metaphases in two rounds using probes for AML1/ETO followed by CEP 6.
Results: FISH results showed the presence of a variant signal pattern for translocation AML1/ ETO. Karyotyping of Giemsa-banded metaphases showed suspicion of a three way translocation t (8;6;21) (q22.1;q27;q22.2) which was confirmed by reflex FISH analysis.
Conclusions: In cases with suspicion of a cryptic three way translocation, reflex FISH on previously Giemsa-banded metaphases gives a clue about the additional partner chromosome which can be different in each case.
Corresponding Author : Prochi F. Madon, Genetics Lab, 6th Floor, Dept. of Assisted Reproduction and Genetics, Jaslok Hospital and Research Centre, 15, Dr. G. Deshmukh Marg, Mumbai, Maharashtra 400026, India.