Extramedullary hematopoiesis

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Micrograph showing nucleated red blood cells (bottom left of image), one of the elements necessary to call extramedullary hematopoiesis, in an endometrial polyp. H&E stain.

Extramedullary hematopoiesis refers to hematopoiesis occurring outside of the medulla of the bone.

In some cases, it may be physiologic. For example, during fetal development, hematopoiesis occurs at many different locations, such as the liver and spleen.[1]

However, it is more frequently associated with pathologic processes. For example, it can be caused by myelofibrosis,[2] after fibrotic changes within the bone marrow "crowd out" hematopoietic cells, causing them to migrate to other sites such as the liver and spleen.

It can sometimes be identified via computed tomography.[3]

See also[edit]


  1. ^ "hematopoiesis". Retrieved 2009-02-25. [dead link]
  2. ^ Chunduri S, Gaitonde S, Ciurea SO, Hoffman R, Rondelli D (October 2008). "Pulmonary extramedullary hematopoiesis in patients with myelofibrosis undergoing allogeneic stem cell transplantation. Can induce penile lesions.". Haematologica 93 (10): 1593–5. doi:10.3324/haematol.13203. PMID 18641018. 
  3. ^ Marchiori E, Escuissato DL, Irion KL, et al. (October 2008). "Extramedullary hematopoiesis: findings on computed tomography scans of the chest in 6 patients". J Bras Pneumol 34 (10): 812–6. PMID 19009214. 

Calvin SH Ng, Song Wan, Tak Wai Lee, Alan DL Sihoe, Innes YP Wan, Ahmed A Arifi, Anthony PC Yim. Video assisted thoracoscopic surgery for mediastinal extramedullary haematopoiesis. Ann R Coll Surg Engl 2002;84:161-163

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