Transposition of 9q34 and 22 (q11toqter) regions has a specific role in chronic myelocytic leukemia.

Six cases are reported of variant Ph' translocations found among 240 patients with Ph'-positive CML. Five cases had a three-chromosome rearrangement involving, in addition to chromosomes 9 and 22, chromosomes 7, 4, 2(two), and 3, respectively, and one case had a two-chromosome rearrangement 22/5. A review of the literature revealed that three- and two-chromosome variant Ph' translocations are observed with equal frequency. It is postulated that all variant translocations are indeed three-chromosome rearrangements, that the specific event for the formation of the Ph' chromosome is the reciprocal translocation 9/22, and that the transposition of regions 9q34 and 22 (q11toqter), plays a major role in the development of CML.