Core-binding factor acute myeloid leukemia (AML) is cytogenetically defined by the presence of t(8;21)(q22;q22) or inv(16)(p13q22)/t(16;16)(p13;q22), commonly abbreviated as t(8;21) and inv(16), respectively. In both subtypes, the cytogenetic rearrangements disrupt genes that encode subunits of core-binding factor, a transcription factor that functions as an essential regulator of normal hematopoiesis. The rearrangements t(8;21) and inv(16) involve the RUNX1/RUNX1T1 ( AML1-ETO ) and CBFB/MYH11 genes, respectively. These 2 subtypes are categorized as AML with recurrent genetic abnormalities, and hence the cytogenetic fusion transcripts are considered diagnostic of acute leukemia even when the marrow blast count is less than 20%. The t(8;21) and inv(16) subtypes of AML have been usually grouped and reported together in clinical studies; however, recent studies have demonstrated genetic, clinical, and prognostic differences, supporting the notion that they represent 2 distinct biologic and clinical entities. This review summarizes the spectrum of this subset of AMLs, with particular emphasis on molecular genetics and pathologic findings.
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