Megakaryocyte emperipolesis

The images show intact malignant B-ALL cells penetrating normal megakaryocytes 

• What is emperipolesis? It is the active penetration of one haematopoietic cell by another cell, which remains intact 
• It is not the same as phagoctosis. The integrity and viability of the engulfed cell differentiates the process from phagocytosis in which lysosomal enzymatic destruction ensues, and entosis involving cells penetrating other cells with delayed cell death occurring
• Emperipolesis involving megakaryocytes can be seen in the normal bone marrow, and pathological states
• One explanation is the mechanism acts as a potential ‘transmegakaryocytic’ route of entry of haematopoietic cells into bone marrow sinusoids and the peripheral circulation
• The clinical significance of this finding is unclear

Credit: Gurney et al, 2020, BJHaem https://doi.org/10.1111/bjh.16277

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