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Skin / Soft Tissue Tumors
Deep benign fibrous histiocytoma
Author: Nat Pernick, M.D., PathologyOutlines.com, Inc.
Reviewer: David Lucas, M.D., University of Michigan Health Systems (January 2009)
Revised: 26 June 2009, last major update June 2009
Definition
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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
● Head and neck and lower limb
Clinical
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● Rare, <1% of fibrohistiocytic tumors
Treatment and prognosis
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● Excision; may recur if incompletely excised, rare metastases
Gross description
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● Well circumscribed with pseudo-capsule, typically 4 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, and 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
● No/rare necrosis or angiolymphatic invasion
Micro images
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Circumscribed tumor Cellular tumor Tumor with more
with no trapped fat fibrous stroma
Presence of foam cells Focal storiform pattern Hemangiopericytoma
helps distinguish from and uniform cellularity like vascular pattern
DFSP
HPC-like Spindle cells (arrow), hemosiderin
vascular pattern (wide arrow) and mild atypia
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 (DFSP) - not circumscribed, usually infiltrative borders, “tight” storiform pattern, uniform cellularity, usually no foam cells, strongly CD34+, Factor XIIIa weak/negative (Semin Cutan Med Surg 1999;18:91)
● Solitary fibrous tumor - patternless (not storiform), alternating hypo- and hypercellular areas, prominent collagen fibers, no histiocytes, strongly CD34+
Additional references
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● AJSP 2008;32:354, AJSP 1994;18:677, AJSP 1990;14:801, Stanford University
End of Skin / Soft Tissue Tumors > Deep benign fibrous histiocytoma
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