Two cases of acute myeloid leukemia with t(11;17) associated with varying morphology and immunophenotype: rearrangement of the MLL gene and a region proximal to the RARα gene

This report describes 2 cases of acute myeloid leukemia (AML), which based on the WHO classification would be classified as AML with an 11q23 (MLL) abnormality, but with contrasting morphologic and immunophenotypic profiles. One case had monocytic features (morphologically and immunophenotypically) with a t(11;17)(q23;q21), a previously identified variant translocation in acute promyelocytic leukemia (APL). The second case had morphologic and immunophenotypic features of APL associated with a t(11;17)(q23;q25). In both cases, fluorescence-in-situ hybridization (FISH) analysis demonstrated that the 11q23 breakpoint involved the MLL gene, but RARα was not involved in the 17q breakpoints. These cases illustrate the importance of FISH analysis to confirm the presence of a particular recurring rearrangement.