Extramedullary Hematopoiesis


EMH With Megakaryocyte
This is a skin biopsy specimen with extramedullary hematopoiesis (EMH), as evidenced by the large megakaryocyte image.



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EMH With Erythroid Cells
This cutaneous lesion contains small clusters of nucleated red blood cells image, which were positive for a hemoglobin A immunostain (not shown).

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Factor VIII Immunohistochemistry
This is a factor VIII immunostain in EMH of the skin. The megakaryocytes are positive for factor VIII. Other megakaryocyte markers include CD61, CD34, and LMP.

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Hemoglobin A Immunohistochemistry
This is a hemoglobin A immunostain in a skin biopsy specimen with EMH; the stain is highlighting erythroid cells.


TERMINOLOGY


Abbreviations




• Extramedullary hematopoiesis (EMH)


Definitions




• Formation of blood cells (including nucleated red blood cells, lymphocytes, and megakaryocytes) outside of bone marrow
image Occurs most commonly in liver and spleen

– Also found in other organs, including lymph nodes, kidney, adrenal, gastrointestinal tract, lung, breast, central nervous system

image Hematopoiesis occurs in skin early in embryonic life


ETIOLOGY/PATHOGENESIS


Viral Infection




• Has been reported in skin in neonates with intrauterine viral infections including
image Cytomegalovirus

image Coxsackievirus

image Rubella


Hematopoietic Disorders




• In neonates, EMH occurs in congenital hematologic disorders including
image Hemolytic disease of newborn

image Twin transfusion syndrome

• In adults, EMH is seen with hematopoietic disorders
image All myeloproliferative neoplasms are associated with EMH
– Primary myelofibrosis is most common, especially in patients who have had splenectomy

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Extramedullary Hematopoiesis

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