Philadelphia chromosome-negative chronic myelogenous leukaemia: a morphological reassessment.

Morphological re-examination of 25 cases classified as Ph1-negative chronic myelogenous leukaemia (CML), with particular attention to the recent French-American-British (FAB) group proposals for the diagnosis of the myelodysplastic syndromes, led to reclassification of all but one of these cases. Upon review of pretreatment material, seven of the 25 cases (28%) were considered to represent myeloproliferative and reactive conditions other than CML. Of the remaining 18 cases, 17 (94%) were reclassified as myelodysplastic syndromes (MDS). These included one case of refractory anaemia (RA), three of refractory anaemia with excess of blasts (RAEB), four of RAEB in transformation (RAEBT), and nine of chronic myelomonocytic leukaemia (CMMoL). Haematological findings in these 17 patients were compared to those in 50 randomly selected patients with Ph1-positive CML. Whereas an absolute basophilia in the peripheral blood was a nearly constant feature in the Ph1-positive group, it was lacking in all but one of the patients with myelodysplastic syndromes. Differences in the pattern and degree of dysplasia were also noted. Only one of the 25 cases studied was considered morphologically and clinically indistinguishable from Ph1-positive CML. It appears that Ph1-negative CML constitutes a heterogeneous group of prognostically distinct disorders and that, in most instances, careful morphologic examination will permit precise classification.