18 Myelodysplastic syndromes

Myelodysplastic syndromes (MDSs) are acquired clonal hematological disorders characterized by normocellular/hypercellular marrow, ineffective hematopoiesis that leads to progressive cytopenia, and dysplasia in peripheral blood, reflecting maturation defects in erythrocytes, leukocytes, and/or platelets.

MDSs are heterogeneous and have a multitude of expressions; however, two morphologic findings are common to all types of MDS: the presence of progressive cytopenias in spite of a cellular bone marrow and dyspoiesis in one or more cell lines. Subtypes of the 2008 World Health Organization classification of MDSs are listed in Box 18-1.

BOX 18-1 World Health Organization Classification of Myelodysplastic Syndromes (2008)

Refractory cytopenia with unilineage dysplasia

Refractory anemia with ringed sideroblasts

Refractory cytopenia with multilineage dysplasia

Refractory anemia with excess blasts

Myelodysplastic syndrome with isolated del(5q)

Myelodysplastic syndrome, unclassifiable

Childhood myelodysplastic syndrome (provisional)

From Swerdlow SH, Campo E, Harris NL, et al, editors: WHO classification of tumours of haematopoietic and lymphoid tissues, ed 4, Lyon, France, 2008, IARC Press.

Dyserythropoiesis

FIGURE 18–1A Oval macrocytes (PB ×1000).

FIGURE 18–1B Dimorphic erythrocyte population (PB ×500).

FIGURE 18–1C Nucleated erythrocyte with abnormal nuclear shape (PB ×1000).

Evidence of dyserythropoiesis (Figure 18-1, A-I) may include any or all of the following: oval macrocytes, hypochromic microcytes, dimorphic erythrocyte population, erythrocyte precursors with more than one nucleus, abnormal nuclear shapes, nuclear bridging, uneven cytoplasmic staining, and/or ringed sideroblasts.