OBJECTIVETo investigate the biological difference of clonal cells between myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML).

METHODBone marrow (BM) clonal cells (which had cytogenetic markers detected by FISH assay) and blasts were quantitatively analysed in 51 MDS and 11 AML patients. The clonal cell percentage in orthochromatic normoblasts, granulocytes and megakaryocytes were assayed. The biological functions for phagocytosis and oxidation of MDS peripheral blood (PB) neutrophils were compared with that of normal controls.

RESULTSAlmost all MDS patients BM had a higher clonal cell percentage (mean 48.2%) than blasts percentage (mean 6.7%) (P < 0.01), but with the subtype of MDS advancing this percentage gap was closing up, and in 11 AML patients no such gap was observed. This gap in MDS patients with + 8 abnormality was smaller than in those with 5q -. In MDS BM, clonal cells were detected in segmented granulocytes (mean 45.9%), orthochromatic normoblasts (mean 46.0%) and mature megakaryocytes (mean 38.0%). In Addition, an approximate amount of clonal cells with the same karyotype abnormality in BM were detected in MDS PB (mean 37.3% in blood vs 48.6% in marrow). Functional analysis showed that the neutrophils in MDS PB could exert nearly normal physiological functions (P > 0.05), but those from AML could not as compared to healthy donors (P < 0.01).

CONCLUSIONThere is a significant difference in the biological features between MDS and AML clonal cells.