Primary Hematopoietic and Lymphoid Tissue ›› Bone Marrow ›› Myeloid ›› Granulocytes & Precursors ›› Normal
Metamyelocyte
›Microscopic Features:
- 2-3x larger than a mature RBC
- Intermediate nuclear to cytoplasmic ratio (more cytoplasm than promyelocyte)
- Kidney bean-shaped Nucleus with nucleus indentation (indentation is less than 1/2 the diameter) and mature chromatin (clumped)
- Perinuclear clearing is common
- Nucleoli are absent
- More cytoplasm with only secondary 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 (~10-15%)
- 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:
Increased number of metamyelocytes are also typically noted in CML patients