Lymphoblastic transformation of Ph1-positive chronic myeloid leukaemia: therapeutic implications and relevance to haemopoietic stem cell theory.

A proportion of patients with blast crisis of CML have blast cells identical to those found in common non-T, non-B all, and whilst this disease is often referred to as lymphoid blast crisis (LBC), evidence is presented that it may in fact arise from a prelymphoid, pre-myeloid (pluripotential) stem cell. Recently developed membrane and enzyme markers (anti-ALL antiserum, TdT assay) have provided convenient diagnostic tests for the detection of LBC. The clinical and haematological features of LBC are reviewed: patients with LBC show a higher response rate to therapy with vincristine and prednisolone, and their survival may be significantly prolonged. The frequent occurrence of meningeal leukaemia suggests the need for prophylactic CNS therapy in LBC patients achieving remission.