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

Promonocyte*


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› 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 [Compare]
• Myeloblast [Compare]
• Mature Monocyte [Compare]
• Reactive lymphocyte [Compare]
• 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

› 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