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Chronic Myeloid Neoplasms

Myelodysplastic syndromes

Refractory Anemia with Excess Blasts (RAEB)

Reviewer: Nikhil Sangle, M.D. (see Reviewers page)
Revised: 12 August 2011, last major update August 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.


● Myeloblasts are 5-19% of bone marrow differential
● Usually cytopenias in 2 or 3 lineages
● Considered high risk MDS
● Type 1: 5-9% blasts in bone marrow or 24% blasts in peripheral blood, no Auer rods, < 1 billion/L monocytes
● Type 2: 10-19% blasts in bone marrow or 519% blasts in peripheral blood or Auer rods in any MDS (Am J Clin Pathol 2005;124:191), < 1 billion/L monocytes; more aggressive, greater tendency to progress to AML
● Refractory anemia with excess blasts in transformation (RAEB-T): classified as AML under WHO classification
● Median survival of 16 months for RAEB-1 and 9 months for RAEB-2 (Br J Haematol 2006;132:162)


● Anemia (normochromic, normocytic or macrocytic), usually neutropenia and thrombocytopenia

Case reports

● Extensive myocardial infiltration (BMC Blood Disord 2006;6:4)
● Cutaneous involvement (Cutis 2007;80:223)

Micro description

Peripheral blood: nucleated red blood cells, immature granulocytes, neutrophilic hyposegmentation, pseudo-Pelger-Huet cells and hypogranulation, myeloblasts 2-4% (RAEB-1) or 519% (RAEB-2), occasional micromegakaryocytes
Bone marrow: normocellular or hypercellular; hyperplasia of granulocytes or erythrocytes; myeloblasts comprise 5 9% (RAEB-1) or 10 -19% (RAEB-2) of white blood cells; Auer rods often seen; severe dysplastic changes in all 3 lineages, more severe than other MDS; abnormal localization of immature precursors (ALIP/clusters or aggregates of blasts located away from bone trabeculae and vascular structures); may have increased reticulin fibers

Micro images

Peripheral blood:

Neutrophil has hypogranular cytoplasm

Neutrophil has hypogranular cytoplasm and bilobed, pseudo-Pelger-Huet nucleus

Bone marrow smear:

Blast in center with adjacent hypogranular neutrophils, erythroid precursor with multiple nuclear fragments in upper left

Large neutrophil (upper right) is hypogranular with marked nuclear hyperlobulation, also single myeloblast with prominent nucleolus and two neutrophils with markedly hypogranular cytoplasm

Promyelocytes and myelocytes, and two myeloblasts on right

Various images


Blood, marrow and myocardial infiltration


Auer rod present in blast, 6-8% myeloblasts, neutrophils show nuclear hypolobulation

RAEB-2: 47 year old woman with 12% myeloblasts and occasional Auer rods:

#1-normocellular biopsy
#2-normal erythroid precursors but shift to immature granulocytes
#3-same patient 4 years later has slightly more cellular marrow
#4-high power of #3 shows more immature granulocytes than 4 years prior

RAEB-2: 62 year old man with pancytopenia, and subsequent AML-M2:

Left: marked fibrosis with streaming effect plus mature megakaryocytes, some in clusters, no shift to immaturity identified
Right: bone marrow aspirate produced only a few cells, including this blast with an Auer rod


● No specific abnormality (Atlas of Genetics and Cytogenetics)

Differential diagnosis

Copper deficiency: reduced copper levels (Leuk Res 2008;32:495)

End of Chronic Myeloid Neoplasms > Myelodysplastic syndromes > Refractory Anemia with Excess Blasts (RAEB)

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