Two preB-ALL samples showed deletion of IKZF1 exons 4–6 (Additional file 7: Table S3); which have been reported in 9% of B-ALL patients [12] and results in expression of the dominant negative form of the transcription factor IKAROS lacking DNA binding zinc finger motifs [13]. Here, IKZF1 is linked to precursor B-cell acute lymphoblastic leukemia.