Renal extramedullary hematopoietic tumor diagnosed by fine needle aspiration: a case report

Extramedullary Hematopoiesis: Cytomorphologic, Histologic, and Radiologic Findings in Sixteen Cases

BACKGROUND

We report a case series of extramedullary hematopoiesis (EMH) diagnosed from the fine needle aspiration (FNA) procedure. Unanticipated EMH is a markedly rare diagnosis that typically presents as a solitary mass of undetermined significance. As such, knowledge of cytopathologic characteristics as well as clinical and radiologic correlates of EMH is paramount.

METHOD AND MATERIAL

A total of 16 EMH cytopathologic cases were seen at the Johns Hopkins Hospital in the past 22 years.

RESULTS

Median age at diagnosis was 61 years and there was no gender bias (male-to-female ratio: 1:1). Presenting signs and symptoms varied widely, from incidental radiographic findings to hemiparesis. Likewise, presumptive clinical diagnoses in 11 of the 16 cases were benign and the other 5 were considered malignant prior to the diagnostic FNA. The most common anatomic site for EMH was the liver, followed by the presacral soft tissue and pleura. While most EMH nodules were singular, a few presented with as many as three radiographically distinct nodules. The average EMH nodule measured 2.8 cm; the EMH liver nodules were larger and measured 4.3 cm on average (p = 0.0043).

CONCLUSION

We share here the salient clinical and radiologic findings and the diagnostic cytopathologic features of EMH in an effort to familiarize the pathologist/cytotechnologist community with this fascinating albeit rare entity.

Contrast-enhanced ultrasound findings in a case of renal extramedullary hematopoiesis

We present the case of an 80-year-old man with two renal solid masses found at sonography, which were imaged by contrast-enhanced ultrasound, CT, and MRI and confirmed histologically. Contrast-enhanced ultrasound findings suggested a benign mass and a CT-guided biopsy yielded a diagnosis of extramedullary hematopoiesis.

Pure erythropoiesis in clear cell renal cell carcinoma

Extramedullary hematopoiesis (EMH) is a phenomenon in which benign immature hematopoietic cells are found in sites other than the bone marrow. Although usually associated with an underlying hematologic abnormality such as myelofibrosis, it can be found in some physiologic states or occasionally within solid tumors. In most instances, foci of EMH contain elements of all cell lineages. Presented here is the second reported case of EMH occurring in a low-grade clear cell renal cell carcinoma in a patient without evidence of hematologic disease. As previously, it manifested as pure erythropoiesis as confirmed by morphology and immunohistochemistry. It is possible that this finding is related to erythropoietin secretion by the tumor and not hematologic malignancy.

Sustained exposure to nicotine leads to extramedullary hematopoiesis in the spleen

The effect of sustained exposure to nicotine, a major constituent of cigarette smoke, on hematopoiesis in the bone marrow (BM) and spleen was evaluated in a murine model. BALB/c mice were exposed to nicotine subcutaneously using 21-day slow-release pellets. Exposure to nicotine had no effect on the proliferation of long-term BM cultures or on their ability to form colonies. However, there was a significant decrease in the generation of lineage-specific progenitor cells, specifically eosinophil (colony-forming unit [CFU]-Eos) progenitors, in the BM of nicotine-exposed mice compared with control mice. Surprisingly, sustained exposure of mice to nicotine was found to induce significant hematopoiesis in the spleen. There was a significant increase in total colony formation as well as eosinophil-, granulocyte-macrophage-, and B-lymphocyte-specific progenitors (CFU-Eos, CFU-GM, and CFU-B, respectively) in nicotine-exposed mice but not in control mice. Sustained exposure to nicotine was associated with significant inhibition of rolling and migration of enriched hematopoietic stem/progenitor cells (HSPCs) across BM endothelial cells (BMECs) in vitro as well as decreased expression of beta2 integrin on the surface of these cells. Although sustained exposure to nicotine has only a modest effect on BM hematopoiesis, our studies indicate that it significantly induces extramedullary hematopoiesis in the spleen. Decreased interaction of nicotine-exposed HSPCs with BMECs (i.e., rolling and migration) may result in altered BM homing of these cells, leading to their seeding and proliferation at extramedullary sites such as the spleen.

Mass-forming extramedullary hematopoiesis diagnosed by fine-needle aspiration cytology

Extramedullary hematopoiesis (EMH) is usually a microscopic finding. However, it may present as a mass-forming lesion making it amenable to fine-needle aspiration biopsy (FNAB). When mass-forming EMH occurs, it can simulate a neoplasm clinically and radiologically. Additionally, the megakaryocytes can mimic malignant neoplastic cells, particularly if EMH is not a considered diagnosis. We report six cases of mass-forming EMH diagnosed by FNAB and evaluate the utility of FNAB in diagnosing EMH. Four patients had prior diagnoses of hematologic disorders, one patient had malignant mastocytosis who presented with lymphadenopathy and one patient had a history of carcinoma. The patients' ages ranged from 46 to 78 yr with an equal sex distribution. Aspirate smears showed trilineage hematopoiesis. The cytomorphologic differential diagnosis included metastatic carcinoma, Hodgkin lymphoma and myeloid sarcoma. No special stains were necessary due to the classic cytologic findings and prior hematologic history.