Interstitial insertion of AF10 into the ALL1 gene in a case of infant acute lymphoblastic leukemia

The ALL1 gene at 11q23 is a promiscuous gene participating in chromosomal abnormalities of acute leukemias with 1 of over 30 potential partner genes. Among these, the AF10 gene at band 10p12 has been recently cloned and characterized. Acute leukemias with the ALL1/AF10 chimeric gene frequently show heterogeneity in the breakpoints on 10p, as well as complex insertion (10;11) as a result of complex molecular mechanisms leading to the ALL1/AF10 fusion. In this context, we report the first description of an infant acute lymphoblastic leukemia with an interstitial insertion of the AF10 gene into the 11q23 band, resulting in the transcription of the ALL1/AF10 fusion product. Furthermore, we show how different diagnostic tools such as molecular, cytogenetic, and fluorescence in situ hybridization (FISH) analyses should be combined to resolve complex situations in the 11q23 setting.