Uterine extramedullary hematopoiesis: What is the clinical significance?

Extramedullary hematopoiesis (EMH) represents abnormal development and growth of hematopoietic tissue outside the bone marrow. Recent studies have shown its association with myelofibrosis and myeloid metaplasia, chronic myeloproliferative disorders, and other hematologic malignancies in up to two-thirds of the cases. Eleven cases of uterine EMH (UEMH) have been reported earlier; of these half had a concurrent, or subsequently developed a clinically significant hematologic disorder. We studied a larger group of patients with UEMH to understand the relationship with hematologic disorders.Cases diagnosed as UEMH between 1995 and 2007 were retrieved from our files (n=20).UEMH was confirmed in all 20 cases. Eighteen cases were located in the fundus including 5 in endometrial polyps and 5 in leiomyomas. Two foci were located within the cervix. The erythroid lineage was present in all foci; 35% also had myeloid precursors, and 2% had megakaryocytes. Twelve of 20 patients had underlying anemia (mean Hgb of 11 mg/dL, range: 5.5 to 15.7 mg/dL). No preexisting hematologic malignancy was identified in any of the patients. Follow-up information was available on 17 patients (mean: 2.88 yr; range: 0.2 to 9yr). None of the patients developed a significant hematologic disorder other than anemia during follow-up.On the basis of our study, UEMH is frequently associated with chronic anemia. In comparison with existing literature suggesting a strong link between UEMH and hematopoietic disorders, our findings suggest that UEMH is rarely associated with serious underlying hematologic conditions and therefore does not warrant extensive hematologic workup.