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Soft Tissue Tumors

Fibrohistiocytic

Cellular 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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● More cellular than classic fibrous histiocytoma, elongated cells are arranged in storiform pattern or fascicles

Clinical features
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● 5% of dermal fibrous histiocytomas
● Young or middle-aged adults, 60% men
● Extremities or head and neck are most common

Treatment and prognosis
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● Excision
● 26% recur (Am J Surg Pathol 1994;18:668)
● Rare metastases (Am J Surg Pathol 1996;20:1361)

Gross description
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● Up to 2.5 cm, rarely can be giant and multinodular mimicking dermatofibrosarcoma protuberans

Micro description
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● Fascicular or storiform but no “tight” storiform pattern
● Cells are plumper than DFSP, with eosinophilic cytoplasm and tapering nuclei; may entrap dermal collagen
● Mean 3 mitotic figures/10 HPF but may be >10 MF/10 HPF
● Extension into subcutaneous fat in 1/3 cases
● At least focal inflammatory cells, foam cells or giant cells
● Epidermal changes in the form of hyperplasia in 58%, focal central necrosis in 12%

Micro images
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Left: storiform growth pattern; right: deep tumor extension


More cellular than classic fibrous histiocytoma


Elongated cells are arranged in fascicles or a storiform pattern


Tumor cells are more histiocyte-like and foam cells are present

● Other images: hyperplastic and acanthotic epithelium;   spindled tumor resembles a leiomyoma

Positive stains
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● Vimentin, CD163, CD68 (83%, J Cutan Pathol 2006;33:353)
● CD63/NKI-C3 (50%), Factor XIIIa (48%), focal smooth muscle actin
● HMGA1, HMGA2, CD10, focally CD34+

Negative stains
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● CD117 (J Cutan Pathol 2007;34:857), CD34, desmin, S100, keratin, HMB45

Differential diagnosis
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Dermatofibrosarcoma protuberans: tight storiform pattern, less polymorphic, cells more spindly than cellular fibrous histiocytoma, CD34+ (strong), Factor XIIIa negative
Leiomyosarcoma: smooth muscle morphology with cigar shaped nuclei, more pleomorphism, infiltrative dermal growth, muscle markers+

End of Soft Tissue Tumors > Fibrohistiocytic > Cellular fibrous histiocytoma


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