Skin tumor - Nonmelanocytic - Deep benign fibrous histiocytoma

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Skin - Nonmelanocytic tumors

Other tumors of skin

Deep benign fibrous histiocytoma

Reviewers: Christopher Hale, M.D., Vijay Shankar, M.D. (see Reviewers page)
Revised: 23 October 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Benign fibrous histiocytoma of subcutaneous tissue, deep soft tissue or parenchymal organs, with no dermal involvement (Am J Surg Pathol 1994;18:677, Am J Surg Pathol 1990;14:801, Stanford Medicine)
● Rare painless lesions, <1% of fibrohistiocytic tumors
● Usually adult males > 25 years (range 6-84 years)
● Usually extremities, head and neck, trunk; rarely in deep soft tissue of retroperitoneum, mediastinum or pelvis

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

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

Clinical images
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Nodule in arch of foot

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

Micro description
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● Prominent storiform pattern of uniform spindle cells with ill defined eosinophilic cytoplasm and bland, elongated or plump vesicular nuclei with no atypia
● Often hemangiopericytoma-like vasculature
● Scattered lymphocytes, either multinucleated giant cells, osteoclastic giant cells or foam cells in 59%
● Usually less than 5 mitotic figures/10 HPF
● Stroma is myxoid or hyaline
● Borders are non-infiltrative, with no trapping of fat cells
● Necrosis or angiolymphatic invasion are rare

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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● CD34 (40%), smooth muscle actin (38%)

Negative stains
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● 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 Skin - Nonmelanocytic tumors > Other tumors of skin > Deep benign fibrous histiocytoma

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