MLL rearrangement with t(6;11)(q15;q23) as a sole abnormality in a patient with de novo acute myeloid leukemia: conventional cytogenetics, FISH, and multicolor FISH analyses for detection of rare MLL-related chromosome abnormalities

We report a rare case of acute myeloid leukemia (AML) with t(6;11)(q15;q23) in a 50-year-old female showing a poor prognosis. Bone marrow biopsy revealed markedly hypercellular marrow with infiltrates of myeloblasts, consistent with AML-M2 morphology. The karyotype of this patient was 46,XX,t(6;11)(q15;q23) in all analyzed cells, and the results of fluorescence in situ hybridization (FISH) and multi-color FISH analysis confirmed this unique MLL rearrangement as a sole abnormality. To our knowledge, t(6;11)(q13∼q15;q23) is the most rare type of MLL rearrangement involving the long arm of chromosome 6. Only two cases with t(6;11)(q13;q23) and three cases with t(6;11)(q15;q23) have been reported, but detailed clinical or laboratory data were not available. From this report, it is apparent that in a cytogenetic laboratory, the accurate detection of a rare type of MLL rearrangement is very important in the differential diagnosis, prompt treatment, and prediction of prognosis of leukemias.