Mitotic activity in myeloid leukaemias. A study of 277 cases

The proportions of myeloblasts, promyelocytes, myelocytes and promonocytes within the granulopoietic precursor pool of the bone marrow and mitotic indices (MI) of the precursor cells were determined in 277 patients with various forms of myeloid leukaemias. The MI of the leukaemic patients were significantly lower than those of 20 normals. Thus the median MI in 186 cases of acute myeloid leukaemias was 0.68%, compared with 1.0% in 85 cases of chronic leukaemias and 1.2% in the normals. Separate MI of the different leukaemic precursor cells were counted in 21 cases of acute myeloid leukaemias and these indices were lower than those of the corresponding normal cells. There were significant differences between the different groups and subtypes of leukaemias and it is suggested that mitotic countings might be of diagnostic and prognostic significance.