World Health Organization and international prognostic scoring system: the limitations of current classification systems in assessing prognosis and determining appropriate therapy in myelodysplastic syndromes.

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders with a wide range of clinical and pathologic manifestations. A number of prognostic and morphologic classifications have been developed that can be helpful in terms of defining the characteristics of populations of patients in clinical trials and longitudinal observational studies, and sometimes in allowing comparisons of the outcomes of different treatment approaches. They are less helpful in guiding treatment decisions in individual patients and, unfortunately, provide little insight into the poorly understood biology of MDS. The merits and limitations of these classification systems are discussed.