Cryptic translocation t(5;11)(q35;p15.5) with involvement of the NSD1 and NUP98 genes without 5q deletion in childhood acute myeloid leukemia

The cryptic translocation t(5;11)(q35;p15.5), which creates a NSD1-NUP98 fusion gene, has been associated with a deletion of the long arm of chromosome 5, del(5q), in pediatric acute myeloid leukemia (AML) patients with differentiated phenotype. We screened five pediatric cases of AML with apparently normal karyotype by use of fluorescence in situ hybridization analysis and detected one case with early myeloid phenotype and poor clinical outcome, but with the same breakpoints and no del(5q). These findings point to the involvement of t(5;11) as an early event in leukemogenesis. Screening for this translocation in AML patients with apparently normal karyotype at onset is recommended.