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


Microscopic Features:
  • 2-3x larger than a mature RBC
  • High nuclear to cytoplasmic ratio (but more cytoplasm than Myeloblast)
  • Round Nucleus with immature chromatin (not clumped)
  • Nucleoli are present but less prominent than Myeloblasts
  • Cytoplasm with primary (azurophilic) granules
Normal % blood-PB, marrow-BM, lymphoid tissue-LN:
  • PB: None
  • BM: Scattered (~2-6%)
  • LN: None
May Resemble:
  • Myeloblast
  • Myelocyte
  • Reactive lymphocyte
  • Neurophil with toxic granules
Differential Diagnoses:

If in blood or increased numbers in bone marrow:
Acute promyelocytic leukemia (AKA AML M3)
Myeloproliferative Neoplasms (e.g. CML)
Leukemoid reactions
Post-GCSF therapy

Classic Immunophenotype:
  • CD34-
  • CD117+
  • HLA-DR-
  • CD13+
  • CD33+
  • CD15-/+
Cartoon Image:

  • Scattered promyelocytes can be seen in a normal bone marrow but no auer rods are allowed in normal promyelocytes