Chronic myelogenous leukemia: molecular diagnostic considerations.

Chronic myelogenous leukemia (CML) is associated in 95% of cases with the Philadelphia chromosome (Ph1) by cytogenetic analysis. This acquired karyotypic abnormality is the product of a balanced translocation between the c-abl oncogene on chromosome 9 and the breakpoint cluster region (BCR) gene on chromosome 22. The resulting BCR/c-abl hybrid gene is actively transcribed and is considered essential in the pathogenesis of this disease. Southern blot- and polymerase chain reaction (PCR)-based tests for the detection of this rearrangement have been introduced over the last decade. These molecular tests are useful adjuncts to cytogenetic analysis in CML and may provide useful clinical information in certain instances.