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

Author: Nikhil Sangle, M.D. (see Authors page)

Revised: 3 March 2017, last major update August 2011

Copyright: (c) 2002-2017,, Inc.

PubMed Search: Refractory Anemia Excess Blasts [title] RAEB

Cite this page: Refractory Anemia with Excess Blasts (RAEB). website. Accessed July 23rd, 2018.
Definition / general
  • 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 2 - 4% blasts in peripheral blood, no Auer rods, < 1 billion/L monocytes
  • Type 2: 10 - 19% blasts in bone marrow or 5 - 19% 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
Microscopic (histologic) description
  • Peripheral blood: nucleated red blood cells, immature granulocytes, neutrophilic hyposegmentation, pseudo-Pelger-Huet cells and hypogranulation, myeloblasts 2 - 4% (RAEB-1) or 5 - 19% (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
Microscopic (histologic) images

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Images hosted on PathOut server:

Peripheral blood:

Neutrophil has hypogranular cytoplasm

Neutrophil has hypogranular
cytoplasm and bilobed,

Bone marrow smear:

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

and myelocytes
and two myeloblasts
on right

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


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:

normocellular biopsy

normal erythroid precursors but shift to immature granulocytes

same patient 4 years later has slightly more cellular marrow

high power shows
more immature granulocytes
than 4 years prior

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

marked fibrosis with streaming effect
plus mature megakaryocytes,
some in clusters, no
shift to immaturity identified

bone marrow aspirate
produced only a few cells,
including this blast with
an Auer rod

Images hosted on other servers:


Various images


Blood, marrow and myocardial infiltration

Molecular / cytogenetics description
Differential diagnosis