Myelodysplastic Syndromes

The myelodysplastic syndromes (MDSs) are a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis. Clinically, patients present with cytopenia(s) and a variable probability of progression to acute myeloid leukemia (AML). Pathologically, there are usually dysplastic morphologic features in one or more of the three hematopoietic lineages, with or without an accompanying increase in myeloblasts in the peripheral blood and/or bone marrow, but at a blast percentage lower than the 20% threshold defining AML. MDS can arise de novo or can be therapy related. Accurate diagnosis and classification of MDS require integration of the microscopic examination of well-prepared and well-stained peripheral blood, bone marrow aspirate, and biopsy slides with the clinical history, including medical and family history, and laboratory and cytogenetic results; flow cytometry immunophenotyping and molecular genetic analyses can provide valuable supportive diagnostic data. Multiple prognostic scoring systems have been devised to help in the management of patients with MDS, with additional contribution likely forthcoming from accumulating data on molecular genetic analyses.