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

Myeloblast*






Microscopic Features:
  • 3-4x larger than a mature RBC
  • High nuclear to cytoplasmic ratio (very little cytoplasm)
  • Round Nucleus with immature chromatin (not clumped)
  • Prominent nucleoli
  • Cytoplasm is scant, gray to pale blue and lacks granules
Normal % blood-PB, marrow-BM, lymphoid tissue-LN:
  • PB: None
  • BM: Scattered (~1-3%)
  • LN: None
May Resemble:
  • Promyelocyte
  • Pronormoblast
  • Lymphoblasts
  • Immature B-cell (hematogone)
  • Monoblast
  • Reactive lymphocyte
Differential Diagnoses:

If in blood or increased numbers in bone marrow:
Acute myeloid leukemia (AML)
Myelodysplastic Syndromes (e.g. RAEB-I or II)
Myeloproliferative Neoplasms (e.g. CML with increased blasts)
Leukemoid reactions
Post GCSF therapy

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



Misc:
  • Approximately 1-3% myeloblasts can be seen in a normal bone marrow but no auer rods are allowed in normal myeloblasts