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Soft Tissue Tumors

Fibrohistiocytic tumors

Deep benign fibrous histiocytoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 23 October 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Benign fibrous histiocytoma of subcutaneous tissue, deep soft tissue or parenchymal organs, with no dermal involvement

Epidemiology
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● Usually adult males > 25 years (range, 6–84 years)

Case reports
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● 25 year old women with painful mass in foot (Ann Dermatol 2011;23:S239)

Treatment and prognosis
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● Excision; may recur if incompletely excised, rare metastases (Am J Surg Pathol 2008;32:354)

Clinical features
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● Rare, < 1% of fibrohistiocytic tumors
● Usually extremities, head and neck, trunk (Am J Surg Pathol 1990;14:801)
● Very rarely in deep soft tissue of retroperitoneum, mediastinum, pelvis
● Usually painless

Clincial images
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Erythematous nodule on arch of foot

Gross description
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● Well circumscribed with pseudocapsule, typically 4 cm (range, 0.5-25 cm), variable hemorrhage

Micro description
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● At least focal classic areas of fibrous histiocytoma, including prominent storiform pattern of uniform spindle cells with ill defined eosinophilic cytoplasm and bland, elongated or plump vesicular nuclei with no atypia (Stanford University)
● Often hemangiopericytoma-like vasculature
● Scattered lymphocytes, and either multinucleated giant cells, osteoclastic giant cells or foam cells in 59%
● Usually < 5 mitotic figures/10 HPF
● Stroma is myxoid or hyaline
● Borders are non-infiltrative, with no trapping of fat cells
● No/rare necrosis or angiolymphatic invasion

Micro images
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Circumscribed tumor with no trapped fat


Cellular tumor


Tumor with more fibrous stroma


Foam cells help distinguish from DFSP


Focal storiform pattern and cellular uniformity


Hemangiopericytoma-like vascular pattern

   
Various images

Positive stains
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● Factor XIIIa, smooth muscle actin (38%), rarely CD34

Negative stains
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● CD34, keratin, EMA, desmin, S100

Differential diagnosis
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Dermatofibrosarcoma protuberans: not circumscribed, usually infiltrative borders, “tight” storiform pattern, uniform cellularity, usually no foam cells, not sclerotic, strongly CD34+, Factor XIIIa weak/negative (Semin Cutan Med Surg 1999;18:91, Am J Surg Pathol 1994;18:677)
Nodular fasciitis: loose collagenous stroma, myxoid, mixed inflammatory cells, thin walled blood vessels
Solitary fibrous tumor: patternless (not storiform), alternating hypo- and hypercellular areas, prominent collagen fibers, no histiocytes, strongly CD34+

End of Soft Tissue Tumors > Fibrohistiocytic tumors > Deep benign fibrous histiocytoma


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