We report a case of chronic myelomonocytic leukaemia (CMML), which transformed first into acute myeloblastic leukaemia (AML) and then into acute lymphoblastic leukaemia (ALL). In the AML and ALL phases, chromosome analysis showed a classic Philadelphia chromosome (Ph) t(9;22)(q34;q11). Molecular studies showed breakpoint cluster region rearrangement between exons e1 and a2 compatible with a p190bcr/abl breakpoint as observed in Ph‐positive lymphoblastic acute leukaemia. The minor (m‐bcr) rearrangement was also detected during complete remission.
This observation supports a multistep pathogenesis of leukaemias, and that the p190bcr/abl breakpoint may influence the course of the disease.