Lymphoid transformation in a CML patient in complete cytogenetic remission following treatment with imatinib.

We describe here a patient with Philadelphia (Ph) chromosome-positive chronic myeloid leukemia who achieved a complete cytogenetic response following treatment with imatinib and then progressed abruptly to lymphoid blastic transformation. The sequence of events suggests that at least in some cases patients who respond well to imatinib may still harbor residual leukemia progenitor or 'stem' cells that are susceptible to acquisition of molecular events that underlie progression to advanced phase disease. The case highlights the need for molecular monitoring of responders and the need to develop strategies for reducing to a minimum or totally eradicating leukemia cells.