Primary Hematopoietic and Lymphoid Tissue ›› Bone Marrow ›› 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

Classic Immunophenotype:
  • CD34-
  • CD64+
  • CD14-
  • CD4dim+
Cartoon Image:



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