Chronic myelogenous leukemia with the e6a2 BCR-ABL and lacking imatinib response: presentation of two cases.

The BCR-ABL fusion gene represents the hallmark of chronic myelogenous leukemia (CML) and is derived from a translocation between chromosome 9 and 22. The majority of CML patients have a breakpoint in the major BCR region of the BCR gene giving rise to e13a2 or e14a2 BCR-ABL transcripts. Occasionally, other BCR breakpoints occur. The current report describes two e6a2 CML patients with imatinib treatment failure and unusual disease progression. One patient was Philadelphia chromosome positive and one was Philadelphia chromosome negative with an atypical BCR-ABL rearrangement, ins (22;9).