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Extramedullary hematopoiesis refers to the location of hematopoietic elements in locations other than the bone marrow medullary space. It may be seen in many conditions including chronic anemias, blood dyscrasias such as leukemia, or as an incidental finding.

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Extramedullary Hematopoiesis in the Endometrium

Rosalia M. Valeri, M.D.; Nada Ibrahim, M.B.; Michael T. Sheaff, M.R.C.Path

From the Department of Histopathology, Barts and the London NHS Trust, Royal London Hospital, Whitechapel, London E1 1BB.

Int J Gynecol Pathol 2002;21:178-181 Abstract quote

Extramedullary hematopoiesis (EMH) in the endometrium is an extremely rare occurrence. Four of the eight previously reported cases were related to an underlying hematological disorder, although the remainder had no such relationship.

We describe a case of endometrial EMH associated with retained products of conception after termination of pregnancy. Routinely and immunohistochemically stained slides revealed several collections of normoblasts and granulocytic precursors in the endometrium with synchronous chronic endometritis. Retained chorionic villi were also identified. The patient had no known history of a hematological disorder or systemic disease and no such abnormality was detected after detailed hematological work-up.

Local effects of growth factors on circulating stem cells may play a pathogenetic role in this process, although an association with recent pregnancy in this case suggests that implantation of fetal hematopoietic elements from the fetus or yolk sac may be more likely.

Langerhans cell histiocytosis presenting as blueberry muffin baby.

Shaffer MP, Walling HW, Stone MS.

Department of Dermatology, University of Iowa Hospitals and Clinics, Iowa City, Iowa, USA.

J Am Acad Dermatol. 2005 Aug;53(2 Suppl 1):S143-6. Abstract quote  

Blueberry muffin baby is a descriptive term for purpuric lesions reflective of extramedullary hematopoeisis. The clinical lesions most commonly result from intrauterine infections, such as rubella and cytomegalovirus, and less commonly with malignancy and hematologic disorders. Langerhans cell histiocytosis is a clonal proliferation of dendritic histiocytes in the skin. This has very rarely been associated with a blueberry muffin presentation.

We report the case of a newborn with typical lesions of cutaneous hematopoiesis and lytic bone lesions related to Langerhans cell histiocytosis. At birth, approximately 40 2 mm to 5 mm purpuric, nonblanching macules were scattered on the trunk, extremities, and soles of our patient. Laboratory studies were unremarkable and cultures were negative.

Skin biopsy showed a dermal proliferation of histiocytes staining positive for S100 and Cd1a. Pediatric bone surveys, chest radiographs, and computed tomography scans of the head were normal. Six months later, the skin lesions had resolved, but radiographs revealed lytic bone lesions of the right tibia, right ilium, and left pubic ramus, consistent with skeletal Langerhans cell histiocytosis.
Morphologic and immunohistochemical evaluation of splenic hematopoietic proliferations in neoplastic and benign disorders.

O'malley DP, Kim YS, Perkins SL, Baldridge L, Juliar BE, Orazi A.

1Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.

Mod Pathol. 2005 Dec;18(12):1550-61. Abstract quote  

Spleen is a common site of extramedullary hematopoiesis. Extramedullary hematopoiesis seen in non-neoplastic conditions can occasionally be extensive and raise concerns for a myeloid neoplasm.

We compared the morphologic and immunohistochemical features of splenic hematopoietic proliferations seen in neoplastic myeloid disorders (eg chronic myeloproliferative disorders, myelodysplastic/myeloproliferative disorders and acute myeloid leukemias) to extramedullary hematopoiesis seen in a variety of reactive conditions. In all, 80 spleen specimens were reviewed.

The presence of each marrow-derived lineage, dysplasia and immunohistochemical results were evaluated (CD34, CD117, myeloperoxidase, CD68, p53, TdT, CD42b and hemoglobin). Neoplastic hematopoietic proliferations in chronic myeloproliferative disorders are characterized by trilineage hematopoiesis with significant dysplasia in all cell lineages. Acute myeloid leukemia showed an increase in immature forms, which were highlighted by immunohistochemistry. Reactive extramedullary hematopoiesis showed variability in histologic features.

Post-bone marrow transplant and thrombotic thrombocytopenic purpura/hemolytic-uremic syndrome spleens showed extramedullary hematopoiesis with some morphologic features of immaturity, which could simulate chronic myeloproliferative disorder. However, they lacked characteristic immunohistochemical features of neoplastic myeloid disorders such as positivity for CD34 or CD117.


Sclerosing extramedullary hematopoietic tumor involving lesser omentum and ligamentumteres in liver explant.

Kwon Y, Yu E, Huh J, Lee SK, Ro JY.

Ann Diagn Pathol. 2004 Aug;8(4):227-32. Abstract quote  

A 47-year-old patient who presented with a 2-year history of hepatitis B virus-associated liver cirrhosis underwent a liver transplantation. The explanted liver was grossly enlarged and diffusely cirrhotic. The lesser omentum and ligamentum teres revealed a 4 cm ill-defined mass that, on sectioning, showed a gray-white appearance.

Extramedullary hematopoiesis on a fibrosclerotic background constituted this mass, but there was also extramedullary hematopoiesis within the liver cords and possibly within the omentum. A bone marrow study also showed chronic idiopathic myelofibrosis. Acute rejection ensued despite immunosuppression and the patient continued to deteriorate and expired.

Sclerotic extramedullary hematopoietic tumor is rare, has an unfavorable prognosis, and may mark the end stage of chronic myeloproliferative disorder.

Fibrous hematopoietic tumors arising in agnogenic myeloid metaplasia.

Beckman EN, Oehrle JS.

Hum Pathol 1982 Sep;13(9):804-10 Abstract quote

Tumors of extramedullary hematopoiesis occasionally occur in long-standing cases of agnogenic myeloid metaplasia (AMM) and resemble hypercellular marrow in a connective tissue stroma. Rarely, this type of tumor mass is markedly fibrous and may pose diagnostic difficulty, especially when there is only limited knowledge of a patient's clinical history.

The authors reports two cases of AMM with such a fibrous hematopoietic tumor, occurring in one patient as a pelvic mass and in another as lymphadenopathy and skin nodules. A review of the literature revealed that fibrous hematopoietic tumors associated with AMM arise predominantly in the retroperitoneum, pelvis, mesentery, and pleura.

Features helpful in establishing the diagnosis include longstanding AMM, megakaryocytes and other hematopoietic cells within the fibrous tissue, and lack of atypia in the fibrous tissue. Current evidence suggests that the fibrous component of the masses is reactive and possibly related to stimulation of fibroblasts by humoral substance released from platelets.

Sclerosing extramedullary hematopoietic tumor in chronic myeloproliferative disorders.

Remstein ED, Kurtin PJ, Nascimento AG.

Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905, USA.

Am J Surg Pathol 2000 Jan;24(1):51-5 Abstract quote

Sclerosing extramedullary hematopoietic tumor (SEMHT) occasionally may arise in patients with chronic myeloproliferative disorders (CMPDs). Morphologically, these tumors may be mistaken for sarcomas or other neoplasms, especially if the clinical history is unknown.

We analyzed four cases to identify features to aid in this differential diagnosis. Clinically, there were four men (mean age, 64.5 years), each with a history of CMPD. Grossly, the SEMHTs formed solitary renal or perirenal masses or multiple mesenteric or omental nodules. Morphologically, each SEMHT had a sclerotic to myxoid background with thick collagen strands and trapped fat. Atypical megakaryocytes, maturing granulocytic and erythroid precursors, and few to no blasts were identified in all cases.

The megakaryocytes, granulocytic precursors, and erythroid precursors reacted strongly with antibodies to factor VIII, myeloperoxidase, and hemoglobin, respectively, in immunohistochemical studies performed in selected cases. SEMHT is a rare manifestation of CMPD that may be mistaken for a sarcoma, especially sclerosing liposarcoma, Hodgkin's disease, especially lymphocyte depletion type, or a myelolipoma.

In a myxoid tumor with trapped fat and atypical cells, morphologic and immunohistochemical identification of maturing hematopoietic precursors helps distinguish SEMHT from sarcoma or Hodgkin's disease. The presence of sclerosis and atypical megakaryocytes helps distinguish SEMHT from myelolipoma.

Sclerosing extramedullary hematopoietic tumor.

Yang X, Bhuiya T, Esposito M.

Department of Pathology, Long Island Jewish Medical Center, New Hyde Park, NY.

Ann Diagn Pathol 2002 Jun;6(3):183-7 Abstract quote

A 73-year-old woman presented with abdominal pain, weakness, and weight loss. Pertinent medical history included myelofibrosis, severe anemia, and lumpectomy for breast cancer. Computed tomography showed marked splenomegaly and numerous soft tissue masses in the mesentery. Excisional biopsy of the mass showed an encapsulated tumor with yellow-tan nodular growth pattern.

Microscopically, the tumor was characterized by the presence of bizarre giant cells in background of prominent dense fibrous stroma. The atypical giant cells were positive for FVIII antibody staining. Many other cells were positive for CD43 antibody staining, indicating that the tumor was hematopoietic in nature, so-called sclerosing extramedullary hematopoietic tumor. Extramedullary hematopoiesis is a common phenomenon associated with severe anemia of any cause. When associated with myelofibrosis, however, it has different morphology from extramedullary hematopoiesis of the other causes.

The significance of recognizing sclerosing extramedullary hematopoietic tumor is that it is often mistaken for sarcomas and other malignant neoplasms, especially when the clinical history is unknown.

Cutaneous sclerosing extramedullary hematopoietic tumor in chronic myelogenous leukemia.

Lane JE, Walker AN, Kulharya A, Marzec T.

Section of Dermatology, Department of Medicine, The Medical College of Georgia, Augusta, Department of Pathology, Mercer University School of Medicine, Macon, Section of Cytogenetics, Department of Pediatrics, The Medical College of Georgia, Augusta, Section of Anatomic Pathology, Department of Pathology, The Medical College of Georgia, Augusta, GA, USA

J Cutan Pathol 2002 Nov;29(10):608-612 Abstract quote.

BACKGROUND: Extramedullary hematopoiesis is a well-documented manifestation of chronic myeloproliferative disorders, most commonly seen in chronic idiopathic myelofibrosis (agnogenic myeloid metaplasia), but rarely in chronic myelogenous leukemia. It typically occurs in the spleen and liver, but has also been described in skin. Microscopically, foci of extramedullary hematopoiesis consist of erythroid and myeloid precursors intermixed with megakaryocytes. The megakaryocytes may elaborate fibrogenic cytokines, which induce proliferation of fibroblasts. The term 'sclerosing extramedullary hematopoietic tumor' has been applied to this latter entity and its resemblance to a fibrohistiocytic neoplasm has been noted.

METHODS: We report the case of a 66-year-old man, whose cutaneous sclerosing extramedullary hematopoietic tumor preceded the diagnosis of chronic myelogenous leukemia.

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Last Updated December 6, 2005

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