ABSTRACT
I. INTRODUCTION Today, the myelodysplastic syndromes (MDS) are recognized as a collection of five clinicopathological entities that describe a wide spectrum of clinical manifestations and survival. It was in 1982 that the French-American-British (FAB) cooperative group proposed the five modern entities of MDS based on a structured clinicopathological approach (1). These clinicopathological entities, described in detail in Chapter 1, are: refractory anemia (RA), refractory anemia with ringed sideroblasts (RARS), refractory anemia with excess blasts (RAEB), refractory anemia with excess blasts in transformation (RAEB-t), and chronic myelomonocytic leukemia (CMML). Prior to the FAB classification system, the lack of a uniform nomenclature for myeloid disorders contributed to the confusion surrounding these diseases (2). Although not perfect, the FAB system has allowed clinicians and researchers to advance the understanding of the pathogenesis and prognosis of MDS as well as to evaluate the utility of therapeutic interventions.
