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Skin / Soft Tissue Tumors
Benign fibrous histiocytoma (superficial)
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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● Storiform pattern of bland spindle cells and foamy histiocytes centered in dermis with possible extension to subcutis
● Variable hemosiderin, multinucleated giant cells, chronic inflammatory cells and pseudoepitheliomatous hyperplasia
Terminology
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● Also called dermatofibroma (particularly if sclerotic and hypocellular), dermal fibrous histiocytoma
● Part of WHO classification for skin tumors, not soft tissue tumors
● See also Bone, Eye-Conjunctiva, Eye-Orbit and Heart chapters
● See also variants described separately - aneurysmal, angiomatoid, atypical, cellular, epithelioid, juvenile xanthogranuloma
Epidemiology
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● Very common benign, indolent tumor of adults, common site is legs of women 20-50 years old
● May be associated with trauma
● Line of differentiation is uncertain
● Multiple lesions may be associated with immunosuppression (Int J Dermatol 2008;47:723)
Pathophysiology
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● Fibroblasts cause strong expression of keratin 19 by keratinocytes and production of a galectin-1-rich extracellular matrix, which may account for pseudoepitheliomatous hyperplasia (J Dermatol Sci 2009;55:18)
Treatment and prognosis
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● Excision; local recurrence is rare even with involved margins
● Rarely is locally aggressive or metastatic (more common for facial lesions, with extension into subcutis)
Gross description
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● Tan-brown, firm, mobile, painless papule < 2 cm in dermis
● Size varies slightly with time; rarely > 5 cm and plaque-like (Australas J Dermatol 2008;49:106)
● May dimple upon lateral compression; may have overlying scaling
Gross images
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Inward dimpling due to tumor Dimpling when squeezed
binding to subcutis (arrow) along its margins
Source: UAB Source: UCSF
Dermoscopy description
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● Wide range of presentations (Arch Dermatol 2008;144:75)
● Pigment network (72%, 3% are atypical), white scar-like patch (57%), different vascular structures (50%), white network (18%)
● May resemble melanoma
Dermoscopy images
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Pseudonetwork present Central white scar-like patch surrounded by a
pigmented network and many brown globules.
Different patterns Various images
Various images Various patterns
Vascular structures Other structures
Micro description
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● Well defined but non-encapsulated
● Storiform pattern of spindled and bland fibroblasts and histiocyte-like cells in mid-dermis and subcutaneous tissue with infiltrative margins but sparing epidermis
● Spindle cells have scant cytoplasm, thin elongated nuclei with pointed ends
● Nuclei almost touch each other, unlike smooth muscle lesions
● Also foamy histiocytes with variable hemosiderin, some multinucleated giant cells, branching vessels, chronic inflammatory cells, pseudoepitheliomatous hyperplasia and epidermal hyperpigmentation
● Often Touton giant cells (superficial and filled with hemosiderin)
● 2% have 4 or more mitotic figures/10 HPF, but still benign behavior (J Cutan Pathol 2008;35:839)
● See also variants described separately - aneurysmal, angiomatoid, atypical, cellular, epithelioid, juvenile xanthogranuloma
● Rare variants are balloon cell (Am J Dermatopathol 2007;29:197), signet ring (Am J Dermatopathol 2009;31:84)
Micro images
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Tumor is more basophilic Basophilia is due
than surrounding dermis to increased cellularity
Sharp border between Tumor cells are composed
tumor and subcutis of histiocyte-like cells and foam cells
Tumor cells are mostly Fat may be entrapped at edge,
fibrous in this focus but must differentiate from infiltration of DFSP
Randomly arranged foam cells, Foam cells vary from none (top),
fibroblasts and histiocyte-like cells; mixed (middle) to predominating (bottom)
foam cells are somewhat
specific for this lesion
Less common finding of Epithelial hyperplasia-left side shows
predominately foam cells squamous / basaloid differentiation,
and cholesterol clefts right side shows follicular differentiation
Cellularity changes over time Vulvar tumor has uniform spindle cells
from subtle increase in confined to dermis
fibroblasts (fig A) to cellular
tumor (fig B/C) to sclerotic Lesion
(fig D-right side)
Pseudoepitheliomatous Marked hemosiderin-laden
hyperplasia macrophages
Low Ki-67 compared to DFSP and AFX
Other images: tumor with hyperplastic epithelium #1; #2; hyperplastic epidermis and sclerotic stroma #1; #2; #3; foam cells with vacuolated cytoplasm; fibroblastic cells with vacuolated cytoplasm in collagenous stroma; spindle cell nodule; paucicellular dermal tumor; spindle cells in dense collagenous stroma
Positive stains
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● Vimentin, Factor XIIIa
● Also tenascin at dermoepidermal junction (Hum Path 2001;32:50); variable calponin (65%), actin, desmin, myosin
Negative stains
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● CD68, CD34, bcl2
● Ki-67 < 10% (Archives 2006;130:831)
Molecular / cytogenetics
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● Often clonal
Differential diagnosis
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● Atypical fibroxanthoma - characteristic gross appearance, storiform pattern not prominent, marked pleomorphism
● Dermatofibrosarcoma protuberans - “tight” storiform pattern, infiltrative, more cellular, no foam cells, CD34+
● Kaposi’s sarcoma - vascular tumor with red blood cell extravasation
● Leiomyoma or leiomyosarcoma - confusion based primarily on variable staining of benign fibrous histiocytoma for muscle markers
● Malignant fibrous histiocytoma - infiltrative, marked pleomorphism and mitotic activity
● Rosai-Dorman disease - CD68+ histiocytes, not storiform
End of Skin / Soft Tissue Tumors > Benign fibrous histiocytoma (superficial)
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