Myelodysplastic Syndrome

Abstract

The myelodysplastic syndromes (MDS) are clonal hematopoietic stem cell diseases characterized by cytopenia(s) due to ineffective hematopoiesis accompanied by dysplasia in one or more myeloid cell lines and an increased risk of development of acute leukemia. A correct diagnosis and classification of MDS requires integration of morphology with clinical data and ancillary studies including cytogenetics and next-generation sequencing to detect submicroscopic pathogenic variants. Assessment of morphologic dysplasia relies on review of adequately stained peripheral blood smear, bone core biopsy, and bone marrow aspirate smears. In addition, the blast count is predictive of progression to acute leukemia and should be obtained from a careful assessment of 200 cells in the peripheral blood and 500 cells on the bone marrow aspirate. The chapter summarizes morphologic dysplasia for each of the lineages in the context of the diagnostic criteria for the WHO-defined MDS categories (see Table 10.1 and reference [1]). It is now recognized that cytopenia is invariably implicit in the diagnosis of MDS and the clinical behavior is influenced by the number of dysplastic lineages and the blast count [2]. The WHO revision therefore proposes to change the nomenclature to eliminate the use of refractory anemia and refractory cytopenia and replace it with “myelodysplastic syndrome” with further subclassification relying on the dysplastic lineages and the blast count (Tables 10.1 and 10.2) (Figs. 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 10.10, 10.11, 10.12, 10.13, 10.14, 10.15, 10.16, 10.17, 10.18, 10.19, 10.20, 10.21, 10.22, 10.23, 10.24, 10.25, 10.26, 10.27, 10.28, 10.29, 10.30, 10.31, 10.32, 10.33, 10.34, 10.35, 10.36, 10.37, 10.38, 10.39, and 10.40).