This case demonstrates a previously unreported structural abnormality of chromosome 16 in a patient with AML M4, which represents a third mechanism to inv(16)(p13q22) and t(16;16)(p13q22) in producing the CBF beta-MYH11 fusion.     ///    "A unique structural abnormality of chromosome 16 resulting in a CBF beta-MYH11 fusion transcript in a patient with acute myeloid leukemia, FAB M4.. "    ///    CBF beta-MYH11 fusions masked by cryptic translocations at the cytogenetic level have been detected by FISH and PCR techniques.     ///    "Due to the improved prognosis associated with CBF beta-MYH11 fusions compared to the standard risk group for AML, its detection remains important.. "