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Soft Tissue Tumors

Fibrohistiocytic tumors

Angiomatoid fibrous histiocytoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 27 October 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Uncommon variant with thick pseudocapsule, marked chronic inflammatory infiltrate and cystic areas of hemorrhage
● Also called fibrohistiocytic tumor of intermediate malignancy

Terminology
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● First described in 1979 (Cancer 1979;44:2147)
● Formerly called angiomatoid malignant fibrous histiocytoma
● May not actually be fibrohistiocytic - Rosai believes origin is vessel related myoid cells with inflammatory features

Clinical features
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● Teens/young adults, often on extremities in areas of lymphoid tissue (popliteal fossa, decubital fossa) or neck
● Rare in elderly
● Often fever, malaise, anorexia, anemia, paraproteinemia
● Unusual sites: lung, mediastinum, ovary, retroperitoneum, vulva (Mod Pathol 2011;24:1560)

Case reports
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● 8 year old boy with pleomorphic scalp tumor with minimal angiomatoid or lymphoid features (J Cutan Pathol 2008;35:855)
● 23 year old woman with spontaneous perforation of hard palate (Oral Maxillofac Surg 2012;16:237)
● 25 year old man with t(12;22) and intracerebral primary (Am J Surg Pathol 2008;32:478)
● 25 year old man with axillary mass (Rare Tumors 2010;2:e20)
● 28 year old woman with leg tumor with cystic structures of sweat duct origin (Pathol Int 2007;57:513)
● 29 year old man with 7 cm swelling in ankle (Case of Week #239)

Treatment and prognosis
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● Excision; may recur locally (10%), distant metastases are rare (1%, Hum Pathol 1999;30:1336)
● Radiotherapy if wide excision margins are not feasible

Clinical images
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Axillary mass at surgery

Gross description
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● Circumscribed, multinodular or multicystic hemorrhagic mass
● Median 2 cm, usually subcutaneous

Micro description
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● Thick fibrous pseudocapsule surrounds nodules, sheets, short fascicles or whorls of monomorphic bland spindle to ovoid eosinophilic cells
● Often highly cellular with bland histiocytoid cells and hemorrhagic cyst-like spaces, large aggregates of chronic inflammatory cells at edge of tumor in lymphoid follicles
● May have moderate pleomorphism and mitotic activity
● Rare clear cells, rhabdomyoblast-like cells, myxoid change in stroma (Mod Pathol 2011;24:1560)

Micro images
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Resembles out of place lymph node


Chronic inflammatory cells and nodules of cells with round / oval nuclei surround hemorrhagic cystic spaces


Cells surrounding cystic spaces are uniform with round / oval nuclei


Some tumors have moderate pleomorphism


Various images


Mediastinal tumor


H&E and desmin

Cytology description
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● Histiocyte-like cells in clusters or dispersed
● Eosinophilic mesenchymal fragments in bloody background with lymphocytes
● Tumor cells have moderate pleomorphism with abundant fragile cytoplasm and prominent nucleoli (Diagn Cytopathol 2005;33:116)

Positive stains
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● Calponin, CD68
● Variable desmin (40-50%), EMA (40%), CD99 (45%), actin (14%)

Negative stains
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● Factor VIII, CD34, CD31, S100, keratin

Molecular / cytogenetics description
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● Usually t(12;16)(q13;p11) creating ATF1-FUS fusion gene, t(12;22)(q13;q12) creating ATF1-EWSR1 gene, or t(2;22)(q33;q12) creating CREB1-EWSR1 gene (Mod Pathol 2010;23:93, Pathol Oncol Res 2012;18:545, Clin Cancer Res 2007;13:7322, Pediatr Dev Pathol 2009;12:143)
● Note: t(12:22)(q13:q12) also present in GI clear cell sarcoma (Am J Surg Pathol 2008;32:858)

Molecular / cytogenetics images
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FISH


t(12;16) karyotype


Diagram

Differential diagnosis
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Aneursymal variant of benign fibrous histiocytoma: no thick pseudocapsule, no inflammatory cells, no significant pleomorphism
Angiosarcoma: endothelial tufting present, CD31+, CD34+, desmin-

Additional references
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Arch Pathol Lab Med 2008;132:273, Atlas of Genetics and Cytogenetics, Stanford University

End of Soft Tissue Tumors > Fibrohistiocytic tumors > Angiomatoid fibrous histiocytoma


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