Variation of bone marrow CD34+ cell subsets in myelodysplastic syndromes according to who types.

Bone marrow (BM) hematopoietic progenitor cells (CD34+) are a heterogeneous population with varying degrees of commitment and maturation to several cell lineages. In myelodysplastic syndromes (MDS), this population is increased. We examined the major cell types found in the blast gate by flow cytometry in newly diagnosed patients with MDS, compared them to normal BM and studied their variation according to WHO type. Two subsets defined by SSC were found both in normal BM and MDS, corresponding to myeloblasts and B-cell precursors. The number of B-cell precursors among all nucleated cells was equally low, independent of WHO type. However, the subset with an intermediate SSC, but CD117, CD13 and CD19 negative increased with the rise of myeloblasts. Concomitantly, the ratio between CD34+/CD117+/CD34-/CD117+ cells was increased. These two features are consistent with the maturation block occurring in the progression of the neoplastic clone. We conclude that the quantitative analysis of the cell types present in the BM blast gate by flow cytometry is not only important for the diagnosis of MDS in patients with peripheral cytopenias and a normal karyotype, but gives also important prognostic information of the patients.