Primary Hematopoietic and Lymphoid Tissue ›› Bone Marrow ›› Myeloid ›› Granulocytes & Precursors ›› Normal
Myelocyte
›Microscopic Features:
- 2-3x larger than a mature RBC
- Intermediate nuclear to cytoplasmic ratio (more cytoplasm than promyelocyte)
- Eccentrically placed oval Nucleus (No nucleus indentation) with more mature chromatin (clumped)
- Perinuclear clearing is common
- Nucleoli are absent (Note: absent nucleoli from this stage onward)
- More cytoplasm with only rare or absent primary (azurophilic) granules
- Secondary (specific) granules of neutrophilic (lilac), eosinophilic (red-orange), or basophilic (blue) color are present based on precursor type
›Normal % blood-PB, marrow-BM, lymphoid tissue-LN:
- PB: None
- BM: Scattered (~10%)
- LN: None
›May Resemble:
›Differential Diagnoses:
If in blood or increased numbers in bone marrow:
Chronic Myelogenous Leukemia (CML)
Leukemoid reaction
Post-GCSF therapy
Chronic Neutrophilic Leukemia
Chronic Myelogenous Leukemia (CML)
Leukemoid reaction
Post-GCSF therapy
Chronic Neutrophilic Leukemia
›Classic Immunophenotype:
- CD34-
- CD117-
- HLA-DR-
- CD13+
- CD33+
- CD15+
- CD11b+/-
- CD16-
›Cartoon Image:
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›Misc:
Myelocyte bulge (increased myelocytes) is commonly noted in CML patients