FISH analysis confirms t(8;21)/RUNX1-RUNX1T1 fusion in metaphase and interphase cells

The RUNX1T1 (8q22) and RUNX1 (21q22.1) probes are labeled with red (Spectrum Orange) and green (Spectrum Green) fluorochromes, respectively. In metaphase cells from leukemias with the t(8;21), fluorescence in situ hybridization (FISH) tests reveal a typical signal pattern of dual RUNX1-RUNX1T1 fusions on the derivative chromosomes 8 and 21 (panel A, arrows), with red and green signals on the remaining normal homologs. In interphase cells, FISH analysis identifies the RUNX1-RUNX1T1 fusions (panel B, arrows), and further provides information on the frequency of the abnormal population.