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

Hypolobated Megakaryocytes (Increased)*


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› Microscopic Features:

• 8-10x larger than a mature RBC
• Lower nuclear to cytoplasmic ratio because of increased cytoplasm
• Many are hypolobated (1-2 lobes) with a mature (clumped chromatin) Nucleus
• Nucleoli are absent
• Cytoplasm is abundant and light blue and usually lacks granules

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

• PB: None
• BM: Rare Scattered
• LN: None

› May Resemble:

• Megakaryocyte (normal) [Compare]
• Osteoclast
• Histiocytes and macrophages (specially multinucleated forms)
• Osteoblast
• Hodgkin Lymphoma Reed Sternberg cell [Compare]
• Metastatic tumor cells
• Myelocyte [Compare]

› Differential Diagnoses:

Increased numbers in bone marrow: MDS Reactive increase secondary to peripheral destruction of platelets Post Chemotherapy Toxin-induced

› Classic Immunophenotype:

• CD41+
• CD42+
• CD61+

› Cartoon Image:


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› Misc:

• Hypolobated Megakaryocytes may be dysplastic and associated with a myelodysplastic syndrome (MDS) or newly forming megakaryocytes that are the result of a peripheral destruction of platelets (e.g. ITP)