Primary Hematopoietic and Lymphoid Tissue ›› Bone Marrow ›› Normal


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Microscopic Features:
  • 3-4x larger than a mature RBC
  • High nuclear to cytoplasmic ratio
  • Round to slightly Indented Nucleus with immature chromatin (not clumped)
  • Prominent nucleoli
  • Cytoplasm is scant, gray to pale blue (more cytoplasm than a Myeloblast and with rare or absent granules
  • vacuoles are rare but sometimes noted in cytoplasm
Normal % blood-PB, marrow-BM, lymphoid tissue-LN:
  • PB: None
  • BM: 1%
  • LN: None
May Resemble: Differential Diagnoses:

If in blood or increased numbers in bone marrow:
AML: Acute Monocytic Leukemia
AML: Acute Myelomonocytic Leukemia
Chronic Myelomonocytic Leukemia

Classic Immunophenotype:
  • CD34+/-
  • CD64+
  • CD4dim+
  • CD14-
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  • Note: In Monocyte differentiated leukemias, total blast count is equal to Monoblasts + Promonocytes (since promonocytes are equivalent to blasts)

Content Editors/Website Administrators:
Hooman H. Rashidi, MD; John C. Nguyen, MD