Extramedullary Hematopoiesis

Background

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.

GROSS APPEARANCE/
CLINICAL VARIANTS CHARACTERIZATION

GENERAL

VARIANTS

ENDOMETRIUM

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.

HISTOLOGICAL TYPES CHARACTERIZATION

GENERAL

VARIANTS

SCLEROSING EXTRAMEDULLARY HEMATOPOIETIC TUMOR

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.

Rosai J. Ackerman's Surgical Pathology. Eight Edition. Mosby 1996.
Sternberg S. Diagnostic Surgical Pathology. Third Edition. Lipincott Williams and Wilkins 1999.

Commonly Used Terms

Hematology

Last Updated 8/2/2002

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HISTOLOGICAL TYPES	CHARACTERIZATION
GENERAL
VARIANTS
SCLEROSING EXTRAMEDULLARY HEMATOPOIETIC TUMOR
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.

GROSS APPEARANCE/ CLINICAL VARIANTS	CHARACTERIZATION
GENERAL
VARIANTS
ENDOMETRIUM
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.