Identification of a Cryptic t(8;20;21)(q22;p13;q22) Resulting in RUNX1T1/RUNX1 Fusion in a Patient with Newly Diagnosed Acute Myeloid Leukemia.

The detection of recurrent genetic abnormalities in acute myeloid leukemia (AML), including RUNX1T1/RUNX1 gene fusion, is critical for optimal medical management. Herein, we report a 45 year old woman with newly diagnosed AML and conventional chromosome studies that revealed an apparently balanced t(8;20)(q22;p13) in all 20 metaphases analyzed. A RUNX1T1/RUNX1 dual-color dual-fusion fluorescence in situ hybridization (FISH) probe set was subsequently performed and revealed a RUNX1T1/RUNX1 gene fusion. Metaphase FISH studies performed on abnormal metaphases revealed a cryptic, complex translocation resulting in RUNX1T1/RUNX1 fusion, t(8;20;21)(q22;p13;q22). This case study shows the importance of performing FISH studies or other high-resolution genetic testing concurrently with conventional chromosome studies for the detection of cryptic recurrent gene fusions in AML, particularly a focused genetic evaluation such as RUNX1T1/RUNX1 gene fusion, when specific abnormalities involving 8q22 are identified.