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Soft Tissue Tumors

Fibrohistiocytic tumors

Epithelioid fibrous histiocytoma


Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 5 December 2014, last major update August 2012
Copyright: (c) 2003-2014, PathologyOutlines.com, Inc.

General
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● Variant with 50% or more of tumor cells having epithelioid morphology

Epidemiology
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● Mean/median age 40-42 years (Br J Dermatol 1989;120:185)
● No gender preference

Pathophysiology
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● May arise from dermal microvascular unit (J Cutan Pathol 2003;30:415)

Clinical features
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● Uncommon, usually presents as small (0.5 to 2 cm), solitary, very rarely multiple, skin colored elevated nodules
● Usually seen on trunk and extremities, rarely in head and neck regions

Case reports
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● 20 year old man with multiple lesions (Am J Dermatopathol 2008;30:373)
● 60 year old man with scalp lesion (Case of the Week #116)
● Underlying a damaged artery (J Dermatol 2005;32:721)

Treatment and prognosis
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● Excision, only rarely recurs (Histopathology 1994;24:123)

Micro description
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● Often exophytic with epidermal collarette
● Circumscribed with uniform, medium to large angulated epithelioid cells (50%+ of tumor cells) that are often perivascular
● Many binucleated cells are often seen
● May be cellular (Am J Surg Pathol 1994;18:583)
● Periphery shows typical features of dermatofibroma
● Minimal inflammation, no prominent giant cells

Micro images
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Histiocyte-like cells with abundant cytoplasm, no / rare spindle cells


Epithelioid cells in hyalinized stroma


60 year old man with scalp lesion


Left to right: above case is Vimentin+, Factor XIIIa+, CD68-, keratin-. Melan A-


Epithelioid fibrous histiocytoma

● Other images: epithelioid cells with vesicular nuclei

Virtual slides
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40 year old man with exophytic nodule on foot

Positive stains
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● Factor XIIIa, vimentin
● EMA (64%, J Cutan Pathol 2011:38:697)
● CD163 (J Cutan Pathol 2009;36:859)
● Rarely D2-40, smooth muscle actin

Negative stains
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● Keratin, S100, myogenic markers, CD68

Differential diagnosis
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Epithelioid sarcoma: deep seated, granuloma-type clusters with necrosis, more atypia, keratin+, CD163-
Granuloma: epithelioid histiocytes in well formed clusters, surrounded by lymphocytes
Histiocytic sarcoma: marked atypia and mitotic activity
Melanoma: tight clustering of atypical cells, S100+, HMB45+
Rosai-Dorfman disease: multiple skin lesions and adenopathy, histiocytes are S100+ and pleomorphic with emperipolesis, also prominent B cells and plasma cells
Solitary epithelioid histiocytoma: dense eosinophilic and glassy cytoplasm, often with spiked cytoplasmic extensions, variable nuclear grooves and multinucleated cells, frequent lymphocytes and neutrophils, CD68+, CD163+ (Am J Surg Pathol 2006;30:521)
Spitz nevus: nevoid type clusters in periphery with spindle cell component, S100+

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


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