IMMUNOPHENOTYPE OF BLAST CRISIS IN CHRONIC MYELOID-LEUKEMIA

The blast crisis in chronic myeloid leukaemia (CML) is morphologically well defined. The aim of this report was to analyze whether immunophe notyping can divide CML blast crises into subtypes as is done in acute de novo leukaemia, and whether a specific CML pattern exists. Between 1991 and 1997 we reevaluated all the immunophenotypes of patients wit h CML blast crises with special regard to immunological subclassificat ion, expression of CD34, presence of aberrant markers and number of im munological dusters. Twenty-nine CML blast crises were analyzed. Seven teen were myeloid, 11 lymphoid and one biphenotypic. The blast crises were divided into subtypes as de novo acute leukaemias: of the 17 myel oid blast crises 6 were undifferentiated, 5 differentiated and 6 had m onocytic differentiation. in the lymphoid blast crises there were no p ro-B, 8 common-B and 3 mature-B. No T-lymphoid blast crises were obser ved. In 26/29 analyses (90%) CD34 was expressed in the blasts. In 17/2 9 analyses (59%) one or two aberrant markers were found. In summary, i mmunophenotyping is important in distinguishing between myeloid and ly mphoid blast crises. A subclassification, as in acute leukaemias, is p ossible. We found no specific immunophenotypic CML pattern. A study di rectly comparing immunophenotyping of CML blast crises with acute de n ovo leukaemia is planned.