ABSTRACT
The term ‘‘myelodysplastic syndromes’’ (MDS) refers to a heterogeneous group of disorders characterized in most patients by peripheral cytopenias with a hypercellular bone marrow. In 1982, the French-American-British (FAB) group first published their classification scheme in an attempt at placing these diverse disorders into an organized framework to enable investigators to communicate with a common language. The FAB classification was modified in 1985, and, since that time, it has been the universally used categorization of these disorders (1,2). The morphological subtypes designated by the FAB committee included 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). Recently, a World Health Organization (WHO) steering committee proposed modifications of the FAB. The most controversial of these changes was a recommendation to decrease the number of blasts required to distinguish acute myeloid leukemia (AML) from MDS from 30% blasts to 20%. This alteration eliminated
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the category of RAEB-T, which had been added in the 1985 modification. In addition, the WHO committee created a category of MDS/MPD (myeloproliferative disorder) that included those patients with chronic myelomonocytic leukemia (CMML) (3). However, these recommendations have not yet been universally accepted. A major area of concern reflects the fact that the distinction between AML and MDS relates more to the clinical features and the pace of the disease than merely the number of blasts counted in the bone marrow. Moreover, lowering the percentage of blasts to be classified as AML would make it difficult to compare future data with past studies.
