Elsevier

Mayo Clinic Proceedings

Volume 78, Issue 10, October 2003, Pages 1223-1233
Mayo Clinic Proceedings

Original Article
Nonhepatosplenic Extramedullary Hematopoiesis: Associated Diseases, Pathology, Clinical Course, and Treatment

https://doi.org/10.4065/78.10.1223Get rights and content

Objective

To define associated clinical conditions, pathology, natural history, and treatment outcome of nonhepatosplenic extramedullary hematopoiesis (NHS-EMH).

Patients and Methods

We retrospectively reviewed the medical charts of all patients identified as having NHS-EMH from 1975 to 2002. Diagnosis was made by tissue biopsy, fine-needle aspiration biopsy, or radionuclide bone marrow scanning.

Results

We identified 27 patients with antemortem diagnosis of NHS-EMH. The most common associated condition and disease site were myelofibrosis with myeloid metaplasia (MMM) (in 18 patients [67%]) and the vertebral column (in 7 patients [26%]; all involving the thoracic region), respectively. At the time of diagnosis of NHS-EMH, concurrent splenic EMH (in 22 patients [82%]; 15 [56%] had undergone splenectomy) and red blood cell transfusion dependency (in 12 patients [44%]) were prevalent. Of the 27 patients, 9 (33%) required no specific therapy. Specific therapy was radiation (in 7 patients with a 71% response rate) and surgical excision (in 6 patients with a 67% response). Treatment-associated complications were limited to surgery. Radiation therapy was not used in the non-MMM group, but low-dose radiation therapy was used in the MMM group for paraspinal or intraspinal EMH (median dose, 1 Gy; range, 1-10 Gy), pleural or pulmonary disease (median dose, 1.25 Gy; range, 1.00-1.50 Gy), and abdominal or pelvic disease (median dose, 2.02 Gy; range, 1.50-4.50 Gy). Median survival after the diagnosis of NHS-EMH was 13 months in the MMM group and 21 months in the non-MMM group.

Conclusions

This retrospective study suggests that NHS-EMH is rare, is often associated with MMM, and preferentially affects the thoracic spinal region. Asymptomatic disease may require no specific treatment, whereas symptomatic disease is best managed with low-dose radiation therapy.

Section snippets

PATIENTS AND METHODS

After approval of this study by the Mayo Foundation Institutional Review Board, we comprehensively searched the institutional database of medical diagnoses and procedures to identify patients diagnosed with any form of EMH from 1975 to 2002. A retrospective chart review was conducted on all patients identified, focusing on those with NHS-EMH diagnosed antemortem by tissue biopsy, FNA biopsy, or radionuclide bone marrow scanning. Patients diagnosed with NHS-EMH by computed tomography or MRI

Associated Diseases

We identified 510 patients as having been diagnosed with EMH. Twenty-seven patients (5.3%) were diagnosed with NHS-EMH and met inclusion criteria: 18 (67%) had MMM (Table 1) and 9 (33%) had no evidence of MMM (non-MMM) (Table 2). The MMM group consisted of 12 patients (67%) diagnosed with agnogenic myeloid metaplasia (AMM) and 6 (33%) diagnosed with post–polycythemic myeloid metaplasia (PPMM) having progressed from polycythemia vera. The non-MMM group consisted of 3 patients with congenital

DISCUSSION

The occurrence of NHS-EMH is rare, and to our knowledge, this study is the largest description of patients with NHS-EMH diagnosed antemortem. Most cases of NHS-EMH occurred in the setting of hematologic disease, with MMM being the most frequent diagnosis. Only 2 patients had no evidence of hematologic disease. Most patients with NHS-EMH had chronic anemia, with a median hemoglobin value of 9.5 g/dL at the time of NHS-EMH diagnosis. This supports the theory that EMH might be a compensatory

CONCLUSIONS

Nonhematosplenic EMH can arise in a variety of organs, producing various symptoms that are sometimes life-threatening. Although rare, NHS-EMH should be suspected in patients with predisposing conditions such as MMM and PPMM. The etiology of EMH remains to be elucidated. Current theories for the development of EMH fail to account for all cases of EMH, especially those arising outside of the reticuloendothelial system. Therefore, we have proposed that a secreted factor, either aberrantly produced

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    1

    This work was supported by an American Society of Hematology medical student award.

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