Philadelphia positive acute leukaemia with minor breakpoint cluster rearrangement may be a stem cell disease.

The biology of Philadelphia chromosome positive (Ph+) acute lymphoblastic leukaemia (ALL) is the subject of much interest. We present a case of Ph+ ALL with a minor breakpoint cluster (mBCR) rearrangement who subsequently relapsed with Ph+ mBCR+ acute myeloid leukaemia and later with Ph+ mBCR+ acute stem cell leukaemia. This case provides further evidence that Ph+ ALL with a mBCR rearrangement may arise from a pluripotent stem cell with similar potential to that of chronic granulocytic leukaemia to undergo blastic crises with differing lineage characteristics.