Clustering of the WT1 gene mutations in the subgroup of childhood CN-AML. WT1 mutations mainly clustered in the CN-AML subgroup. No mutations were found in the CBF-AML subgroup [ie, t(8;21) and inv(16)], and very few were detected in the t(15;17) and in the MLL gene–rearranged childhood AML cases. Mutations were also found in the subgroup with other karyotypes, but at a lower frequency (14.8%) than in the CN-AML subgroup (22.3%).