Myelodysplastic syndromes with monocytic component: hematologic and cytogenetic characterization.

BACKGROUND AND OBJECTIVE: Patients with myelodysplastic syndromes (MDS) showing high numbers of abnormally localized immature precursors (ALIP) also display myelomonocytic antigens on immature cells, and it has been suggested that the presence of monocytosis could define a distinct subset of MDS characterized by poorer survival. The objective of this study was to analysis the incidence and significance of monocytosis among our series of patients with MDS and correlate the distributions of these elements with other hematologic features.

METHODS: We evaluated the monocytic component in myelodysplastic syndromes in order to clarify the significance of monocytosis in MDS and its relationship with CMMoL and other MDS. Monocytosis was defined as a percentage of blood monocytes greater than 10%.

RESULTS: Among a series of 139 consecutive MDS patients, we describe a group of 29 (20.8%) patients with monocytosis and dysplastic features involving multiple cell lineages which do not fulfill the criteria for diagnosis of CMMoL or aCML. These patients, who do not differ from MDS without monocytosis in the main clinical parameters, are characterized by relatively higher leukocyte (WBC 6.6 x 10(9)/L) and granulocyte counts (PMN 2.5 x 10(9)/L), hypercellular bone marrow and relatively poor prognosis. Among these patients, we observed a particularly high incidence of evolution to CMMoL (34.5%) and AML (17.2%) with monocytic component (FAB M4 and M5). Cytogenetic data demonstrated clonal chromosome changes in 11/13 patients with MDS and monocytosis, while only 19/41 patients without monocytosis showed clonal abnormalities.

CONCLUSIONS AND PERSPECTIVES: The combination of hematologic and cytogenetic features in our study suggests that it is reasonable to consider myelodysplasia with monocytosis as a distinct disease subset of MDS, characterized by multilineage dysplasia along with a higher incidence of karyotype aberrations. The multi-step pathogenetic process in these patients may have reached a more advanced stage at which the relative or absolute increase in the number of monocytes may represent the first event in the subsequent progression of the disease towards acute leukemia.