Commercially available FISH probe systems for the detection of derivative chromosome 9 deletions. Structure of the ABL and BCR loci showing the common breakpoints (arrows) and the probes used in the commercially available probe systems: the extra signal (ES), D-FISH, and dual color, dual fusion detection system (“Methods for detecting deletions”). ASS indicates arginine succinate synthetase; Met 8604, Met 8604 gene; and IGLV, immunoglobulin lambda light chain locus.