MDS classification: an appraisal

Haema 2011; 2(2): 144-152

by Ioannis Kotsianidis, Evagelia Nakou, Paraskevi Miltiadi

Hematology department, Democritus Thrace University, Medical school, Alexandroupolis

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More than 30 years after the first attempt of their classification, Myelodysplastic syndromes (MDS) remain a group of complex and obscure entities. This relates not only to their enigmatic pathobiology, but also to the heterogeneity of patients’ characteristics and comorbidities. Therefore, apart from the diagnostic classifications of MDS, various prognostic systems have also been developed based principally on clinical and histopathological features, whereas the only biological information incorporated into these systems is currently the karyotype. Nevertheless, the WHO classification and the two most widely used prognostic systems, viz IPSS and WPSS, stratify patients according to subjective parameters based on poor biological grounds, like the percentage of blasts, dysplasia and the number of cytopenias, the latter defined via statistical models and thus not reliably reflecting the clinical risk. Moreover, two novel factors render imperative the need for refinement of the current prognostic classifications. The first is the identification of numerous new genetic and epigenetic alterations carrying prognostic information. The second factor is the development of novel targeted therapies based on the better understanding of MDS pathobiology, which may, at least temporarily, modulate the   natural course of the disease. Thus, both the integration of the molecular data and the identification of biomarkers of response to newer agents represent the main challenges in the design of future categorization models of MDS. This review will attempt a critical appraisal of the current classification and prognostic schemes and the emerging biological data with potential prognostic impact.