Ph-negative chronic myeloid leukaemia.

An analysis of five patients with Philadelphia chromosome (Ph) negative chronic myeloid leukaemia (CML) revealed that two were clinically and haematologically identical to Ph-positive CML whereas three should be reclassified as chronic myelomonocytic leukaemia (CMML). At a molecular level the first two patients showed the same juxtaposition of c-abl and bcr genes as is seen in Ph-positive CML. These genomic changes were not seen in the other three patients. Observations on these five patients suggest that the clinical course and prognosis of the rare patient who carries the Ph 'molecular defect' but lacks the Philadelphia chromosome is no different from Ph-positive CML.