Primary Hematopoietic and Lymphoid Tissue ›› Bone Marrow ›› Myeloid ›› Monocytes & Precursors ›› Normal
Promonocyte
›Microscopic Features:
- 3-4x larger than a mature RBC
- Round Indented Nucleus with immature chromatin (not clumped; slightly more mature than monoblast)
- Prominent nucleoli (less prominent than Monoblast)
- Cytoplasm is scant but more than Myeloblasts , gray to pale blue and with rare or no granules
- vacuoles maybe sometimes noted in the cytoplasm
›Normal % blood-PB, marrow-BM, lymphoid tissue-LN:
- PB: None
- BM: 1%
- LN: None
›May Resemble:
- Monoblast
- Myeloblast
- Mature Monocyte
- Reactive lymphocyte
- Lymphoma cell (e.g. Leukemic phase of Burkitt)
- Carcinoma cell
›Differential Diagnoses:
If in blood or increased numbers in bone marrow:
AML: Acute Monocytic Leukemia
AML: Acute Myelomonocytic Leukemia
Chronic Myelomonocytic Leukemia
AML: Acute Monocytic Leukemia
AML: Acute Myelomonocytic Leukemia
Chronic Myelomonocytic Leukemia
›Classic Immunophenotype:
- CD34-
- CD64+
- CD14-
- CD4dim+
›Cartoon Image:
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›Misc:
Note: Promonocytes count as Blasts when looking for total blast count. In Myeloid leukemias with Monocytic differentiation, the total blast count is equal to Monoblasts + Promonocytes