The Proportion of Clonal Divisions Varies in Different Hematologic Malignancies

The detection of clones by conventional cytogenetic studies in diagnostic hematoncology is heavily subject to the effects of many biological and laboratory factors, one of which is the number of divisions analyzed. Data from 20 laboratories were combined to get an impression of the true frequency of clonal divisions for comparison with the theoretical models that have been previously used to set laboratory policies. This study showed that low-percentage clones were more common in the myelodysplastic syndromes and that high-percentage clones were more common in acute myeloid leukemia than in acute lymphoblastic leukemia (ALL), although the clone detection rate in ALLs is higher. The inference is that the putative diagnosis should be taken into account when deciding how many divisions to analyze before concluding that no detectable clone is present.