A complex chromosome rearrangement forms the BCR‐ABL fusion gene in leukemic cells with a normal karyotype

Abstract

Chromosome in situ hybridization studies showed that the normal karyotype of leukemic cells from a patient with Ph¹‐ negative, BCR‐positive chronic myeloid leukemia (CML) concealed a complex t(9;22;20)(q34;q 11;p13). The close association of 5′‐BCR and 3′‐ABL was demonstrated by field inversion gel electrophoresis, and in situ hybridization showed that BCR‐ABL was located on the short arm of chromosome 20. Our findings further indicate that chromosome rearrangement is the cause of BCR‐ABL gene fusion in leukemic cells that show a normal karyotype. Results from in situ hybridization studies were consistent with formation of the t(9;22;20) by a two step chromosomal rearrangement, but field inversion gel electrophoresis results indicated a more complex rearrangement.