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

Megakaryoblast (Increased)*


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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 pale blue with occasional cytoplasmic blebs (want-to-be platelets)

› Normal % blood-PB, marrow-BM, lymphoid tissue-LN:

• PB: None
• BM: Rare (<1%)
• LN: None

› May Resemble:

• Myeloblast [Compare]
• Pronormoblast [Compare]
• Lymphoblast [Compare]
• Immature B-cell (hematogone) [Compare]
• Monoblast [Compare]
• Reactive lymphocyte [Compare]

› Differential Diagnoses:

If in blood or increased numbers in bone marrow: Acute Megakaryoblastic leukemia (AML-M7) Transient Myelopoeisis (usually asosciated with some newborns with Down Syndrome)

› Classic Immunophenotype:

• CD41+
• CD42+
• CD61+

› Cartoon Image:


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› Misc:

• Transient Myelopoeisis shows increased megakaryoblasts in blood and/or marrow of a newborn down syndrome patient and may mimic an AML-M7 (Acute Megakaryoblastic Leukemia)