t(8;21)(q23;q22), a Novel Translocation Involving the RUNX1 Gene in a Patient with Acute Myeloid Leukemia.

Chromosome translocations involving the RUNX1 gene at 21q22 are recurring abnormalities in acute myeloid leukemia (AML). t(8;21)(q22;q22) is the most common translocation involving the RUNX1 gene, which is categorized as an independent type of acute leukemia in the WHO classification system. The translocation results in a frame fusion of RUNX1::RUNX1T1, which is considered to be the pathogenesis of neoplasm development. The present report describes an AML case displaying a t(8;21)(q22;q22)-like translocation by initial chromosome analysis, but subsequent FISH analysis did not show the fusion signals corresponding to the RUNX1::RUNX1T1 fusion gene. Reverse transcriptase polymerase chain reaction (RT-PCR) also failed to identify the formation of the RUNX1::RUNX1T1 fusion gene. Reassessment of chromosome analysis in light of the FISH and RT-PCR data yielded a t(8;21) (q23;q22) translocation.