Clinical

• age 50+
• 40% of MDS
• anemia, thrombocytopenia, neutropenia
• progress to AML (25% RAEB1, 33% RAEB2)
• CD7 = poorer prognosis
• prognosis: RAEB1 > RAEB2 by Auer rod > RAEB2 by blast count

Types

• RAEB1: 5-9% marrow blasts or 2-4% blood blasts
• RAEB2: 10-19% marrow blasts, 5-19% blood blasts, or Auer rods in blast
• RAEBF: myelofibrosis

Morphology

• blood

—- anisopoik

—- giant plt, hypogranular plt

• neutrophils: abnormal granularity, segmentation
• 2-19% blasts
• marrow
  • usually hypercellular, abnormal paratrabecular clustering of erythroids and megas
  • erythroid
    • can be increased
    • macrocytic
    • megaloblastoid
    • abnormal lobation, nuclear bridging
  • granulocytic
    • usually increased
    • small neuts
    • nuclear hypolobation, hypersegmentation
    • cytoplasmic hypogranularity, pseudo Chediak Higashi granules
  • megakaryocyte
    • normal to increased
    • paratrabecular clustering
    • micromegakaryocytes
    • multinucleation
  • 5-19% blasts, tend to localize away from trabeculae and vessels

Immunophenotype

• precursor cells (CD34, CD117)
• myeloid lineage: CD13, CD33
• can have aberrant CD7 (worse prognosis), CD56
• CD61 stains dysplasic megas