Who is WHO in myelodysplastic syndromes? Clinical implications of the WHO classification

Myelodysplastic syndromes (MDS) are a heterogeneous group of neoplastic clonal stem cell diseases characterized by dysplastic morphologic features with a varying percentage of leukemic blasts and clinical bone marrow failure. The French-American-British (FAB) system served as the gold standard of MDS classification for more than two decades. The World Health Organization (WHO) classification, built on the backbone of the FAB classification, is an attempt to further improve the prognostic value of MDS classification as well as to establish its clinical utility as a tool to select different treatments. In this article we highlight the major differences between the FAB classification and the WHO MDS classification. We discuss in more detail the experience of using the new WHO classification since its publication and review the studies that have tried to validate the prognostic value of the new classification or apply it to predict clinical responses to various treatments.