A new t(9;11;20;22)(q34;p11.2;q11.21;q11) in a Philadelphia-positive chronic myeloid leukemia case

The so-called Philadelphia (Ph) chromosome is found in over 90% of cases of chronic myeloid leukemia (CML). Of these cases, 2–10% demonstrate complex translocations involving a third chromosome in addition to chromosomes 9 and 22. Since the majority of CML cases are currently treated with imatinib, variant rearrangements tend to have no specific prognostic significance, although the mechanisms involved in resistance to therapy have yet to be investigated. This study evaluated a CML case with complex chromosomal aberrations not previously observed. A four-chromosome translocation involving chromosomal regions including 11p11.2 and 20q11.21 in addition to 9q34 and 22q11 was characterized in detail using array-proven multicolor banding (aMCB), a technique which has proven to be of significance in characterizing breakpoint regions in detail. Underlying mechanisms and prognostic factors are discussed.