Blood/Blood Cells and Cellular Components ›› Neutrophils ›› Abnormal

Myeloblast*


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› Microscopic Features:

• 3-4x larger than a mature RBC
• High nuclear to cytoplasmic ratio
• 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: 1-3%
• LN: None

› May Resemble:

• Promyelocyte [Compare]
• Pronormoblast [Compare]
• Lymphoblasts [Compare]
• Immature B-cell (hematogone) [Compare]
• Monoblast [Compare]
• Reactive lymphocyte [Compare]

› 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-
• MPO+

› Cartoon Image:


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for direct comparison
› Misc:

• Myeloblast with Auer rod is by definition abnormal and usually represents an underlying AML or high grade MDS (RAEB-II)