Extramedullary haematopoiesis is a response to erythropoiesis failure in bone marrow. Extramedullary haematopoiesis occurs in haemoglobinopathies, myeloproliferative disorders, or bone marrow infiltration. It occurs most often in the spleen and liver and occasionally in the lymph nodes. Less common organs include the pleura, lungs, gastrointestinal tract, breast, skin, brain, kidneys, and adrenal glands.
- myeloproliferative disorders
Where extramedullary haematopoiesis involves an organ, there is usually radiographic evidence of its enlargement, e.g. hepatomegaly, splenomegaly visualised by ultrasound, CT or MRI. Lesions are typically hypermetabolic and hence is FDG-18 avid on PET-CT.4
However, in the less common situation where extramedullary haematopoiesis involves other tissues within the thorax, they can be seen as a posterior mediastinal mass. These are paraspinal masses that may be unilateral or bilateral and have smooth, sharply delineated, often lobulated margins.
- 1. Choi H, David CL, Katz RL et-al. Case 69: extramedullary hematopoiesis. Radiology. 2004;231 (1): 52-6. doi:10.1148/radiol.2311020673 - Pubmed citation
- 2. Gumbs RV, Higginbotham-ford EA, Teal JS et-al. Thoracic extramedullary hematopoiesis in sickle-cell disease. AJR Am J Roentgenol. 1987;149 (5): 889-93. AJR Am J Roentgenol (abstract) - Pubmed citation
- 3. Holden C, Hennessy O, Lee WK. Diffuse mesenteric extramedullary hematopoiesis with ascites: sonography, CT, and MRI findings. AJR Am J Roentgenol. 2006;186 (2): 507-9. doi:10.2214/AJR.04.1788 - Pubmed citation
- 4. Roberts AS, Shetty AS, Mellnick VM, Pickhardt PJ, Bhalla S, Menias CO. Extramedullary haematopoiesis: radiological imaging features. Clinical radiology. 71 (9): 807-14. doi:10.1016/j.crad.2016.05.014 - Pubmed