¹Division of Hematology-Oncology, Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA

²University of Texas Medical School, Houston, TX, USA

Correspondence to: P H Rao, Texas Children's Cancer Center, Baylor College of Medicine, 6621 Fannin St, MC 3-3320, Houston TX 77030-2399, USA; Fax: 832 825-4846

^aPresent address: Children's Mercy Hospital, Section of Medical Genetics and Molecular Medicine, Kansas City, MO, USA

We applied multicolor spectral karyotyping (SKY) to a panel of 29 newly diagnosed pediatric pre B-cell ALLs with normal and abnormal G-banded karyotypes to identify cryptic translocations and define complex chromosomal rearrangements. By this method, it was possible to define all add chromosomes in six cases, a cryptic t(12;21)(p13;q11) translocation in six cases, marker chromosomes in two cases and refine the misidentified aberrations by G-banding in two cases. In addition, we identified five novel non-recurrent translocations - t(2;9)(p11.2;p13), t(2;22) (p11.2;q11.2), t(6;8)(p12;p11), t(12;14)(p13;q32) and t(X;8)(p22.3;q?). Of these translocations, t(2;9), t(2;22) and t(12;14) were identified by G-banding analysis and confirmed by SKY. We characterized a t(12;14)( p13;q32) translocation by FISH, and identified a fusion of TEL with IGH for the first time in ALL. We identified a rearrangement of PAX5 locus in a case with t(2;9)(p11.2;p13) by FISH and defined the breakpoint telomeric to PAX5 in der(9)t(3;9)(?;p13). These studies demonstrate the utility of using SKY in combination with G-banding and FISH to augment the precision with which chromosomal aberrations may be identified in tumor cells.

Leukemia (2002) 16, 2222-2227. doi:10.1038/sj.leu.2402662

spectral karyotyping; chromosomal translocations; pediatric ALL