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Myocardial extramedullary hematopoiesis: a clinicopathologic study
1The Lauren V. Ackerman Laboratory of Surgical Pathology, Barnes-Jewish Hospital, Washington University Medical Center, St. Louis, Missouri 63110, USA.
Summary
Extramedullary hematopoiesis (EMH) is uncommon in adults but frequently found in healing myocardial infarcts. This suggests inflammation- or repair-associated factors, not ischemia, trigger EMH in heart tissues.
Area of Science:
- Cardiovascular Pathology
- Hematology
- Histopathology
Background:
- Extramedullary hematopoiesis (EMH) typically occurs in fetal development or with hematologic disorders.
- EMH unassociated with hematologic disease is rare, with myocardial EMH being an infrequent finding.
Purpose of the Study:
- To determine the frequency and clinicopathologic setting of EMH in myocardial tissues.
- To investigate the association between myocardial EMH and myocardial infarcts.
Main Methods:
- Retrospective examination of 805 consecutive myocardial samples (surgical and autopsy specimens).
- Diagnosis of EMH based on the presence of immature erythroid or myeloid cell clusters.
- Immunoperoxidase studies performed in selected cases to confirm cell types.
Main Results:
- EMH foci identified in 7.2% of surgical and 3.7% of autopsy hearts.
- 65% of EMH-positive cases were associated with myocardial infarcts in various stages of repair.
- EMH was not found in acute infarcts less than 72 hours old, but was present in healing infarcts.
Conclusions:
- Myocardial EMH is relatively common in healing myocardial infarcts.
- EMH in myocardial tissue is rarely found in normal or nonischemic myocardium.
- The findings suggest that inflammation or repair-associated factors, rather than ischemia itself, induce myocardial EMH.