Skin nonmelanocytic tumor
Fibrous, fibrohistiocytic and myofibroblastic neoplasms
Dermatofibroma (fibrous histiocytoma)

Editorial Board Member: Lauren N. Stuart, M.D., M.B.A.
Engy Abdellatif, M.B.B.Ch., M.D., Ph.D.

Topic Completed: 1 June 2017

Minor changes: 21 October 2020

Copyright: 2002-2020, PathologyOutlines.com, Inc.

PubMed Search: Benign fibrous histiocytoma [title]

Engy Abdellatif, M.B.B.Ch., M.D., Ph.D.
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Cite this page: Abdellatif E, Chatzipantelis P. Dermatofibroma (fibrous histiocytoma). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissuebfh.html. Accessed October 24th, 2020.
Definition / general
  • General:
    • Fibrous histiocytomas are benign fibrohistiocytic (BFH) tumors; they are among the most common soft tissue lesions and have these features:
      1. Commonly found on the skin
      2. Slow growing solitary nodule
      3. Made up of a mixture of fibroblastic and histiocytic cells, collagen and blood vessels
      4. Variable hemosiderin, multinucleated giant cells, chronic inflammatory cells
      5. Many variants have been described; more than one variant can be seen in the same lesion
  • Definition:
    • BFH is a neoplastic or quasi neoplastic mesenchymal soft tissue lesion with fibroblastic and histiocytic differentiation; most commonly, this tumor is located in the dermis and subcutis
Essential features
  • Acanthosis or pseudoepitheliomatous hyperplasia of the overlying skin
  • Haphazard / vague storiform pattern of bland spindle cells centered in dermis with possible extension to subcutis
  • Very uncommon infiltration into and around fat cells
Terminology
  • Dermatofibroma when located in the skin
Epidemiology
  • Common
  • All races
  • All ages but more common in the age group from 20 - 49 years
  • Females > Males
  • 1/3 of cases show metachronous multiple tumors
  • Synchronous tumors have been reported in immunosuppressed and SLE patients
Sites
  • Any part of the skin surface can be affected
  • Most common site is extremities
  • Rare sites are conjunctiva and larynx
Pathophysiology
  • Clonal proliferation may be found, but is not a proof of the neoplastic nature of the lesion
  • Factor XIIIa+ dendritic cells are found more consistently in fibrous histiocytoma, but MAC387 (a histiocytic marker) is expressed less consistently
  • The epithelioid and atypical dermatofibroma variants show rearrangement and overexpression of ALK gene
Etiology
  • It is not clear whether fibrous histiocytoma is a reactive or neoplastic process
  • Often seems to appear after a minor injury to the skin such as a prick from a thorn, vaccination or insect bite
Diagrams / tables

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Dermoscopic patterns

Dermoscopic patterns

Clinical features
  • Variable: elevated, pedunculated or dome shaped
  • Atrophic variants are flat and depressed
  • Can have variable color, sometimes pink, pigmented, tanish brown or bluish black
  • Firm in consistency and measures from a few millimeters to a few centimeters in diameter
  • May dimple upon lateral compression; may have overlying scaling
  • Rarely metastasizes (Am J Surg Pathol 2013;37:484)
Case reports
Treatment
  • Typical dermatofibromas are considered benign tumors and the prognosis is excellent
  • Spontaneous regression has been reported in rare occasions and may leave a post inflammatory hypopigmentation
  • Wide excision is adequate to prevent the recurrence of the tumor
  • Local recurrence is rare, even with involved margins
  • Locally aggressive and metastasizing tumors have been reported
Clinical images

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Contributed by Mark R. Wick, M.D.
Breast skin Breast skin

Breast skin



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Dermatofibroma on the skin Dermatofibroma on the skin Dermatofibroma on the skin Dermatofibroma on the skin Dermatofibroma on the skin Dermatofibroma on the skin

Dermatofibroma on the skin


Dermatofibroma on the skin Dermatofibroma on the skin Dermatofibroma on the skin

Dermatofibroma on the skin

Dimpling when squeezed along margins Dimpling when squeezed along margins

Dimpling when squeezed along margins

Dermatofibroma on the right upper back

Dermatofibroma on the right upper back


A very flat dermatofibroma

A very flat dermatofibroma

Dermatofibroma on the arm

Dermatofibroma on the arm

Side on view

Side on view

Dermatofibroma on the waist

Dermatofibroma on the waist

Cellular dermatofibroma

Cellular dermatofibroma

Dermoscopy

Dermoscopy


Dermoscopy images: central scar-like area associated with a peripheral pigment network Dermoscopy images: central scar-like area associated with a peripheral pigment network Dermoscopy images: central scar-like area associated with a peripheral pigment network Dermoscopy images: central scar-like area associated with a peripheral pigment network Dermoscopy images: central scar-like area associated with a peripheral pigment network Dermoscopy images: central scar-like area associated with a peripheral pigment network

Dermoscopy images: central scar-like area associated with a peripheral pigment network


Pseudonetwork present

Pseudonetwork present

Central white,<br>scar-like patch,<br>pigmented network<br>and brown globules

Central white,
scar-like patch,
pigmented network
and brown globules

Dermoscopic appearance

Dermoscopic appearance

Close up

Close up

Various images Various images

Various images

Dermoscopy
  • The tumor has a wide range of presentations
  • The most classic dermoscopic pattern is a pigmented network and central white patch
Gross images

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Ulcerated cutaneous mass

Ulcerated cutaneous mass

Microscopic (histologic) description
  • Heterogeneous tumor, with many variants
  • Nonencapsulated lesion showing extension in the subcutis as radiating spikes
  • Overlying epidermis shows pseudoepitheliomatous hyperplasia and hyperpigmentation of basal cell layer and sometimes the overlying epidermis shows thinning
  • Grenz zone is usually present
  • Mixture of fibroblastic, myofibroblastic-like and histiocytic cells
  • Spindle cells have scant cytoplasm, thin elongated nuclei with pointed ends
  • Nuclei almost touch each other, unlike smooth muscle lesions
  • Arranged in a cartwheel or vague storiform pattern
  • Varying numbers of inflammatory cells, foam cells and siderophages can be seen
  • Touton giant cells may be seen
  • Mitotic figures are uncommon; when seen, tumors still have benign behavior
  • Variants can be categorized based on changes in the architecture, cellular and stromal content or both:
    • Architectural differences:
      • Aneurysmal
      • Atrophic
      • Deep penetrating
      • Palisading
    • Aneurysmal variant: highly cellular with extensive cystic hemorrhage
    • Cellular / stromal content:
      • Atypical: involvement of dermis and superficial subcutaneous tissue by pleomorphic, plump, spindle or polyhedral cells with large hyperchromatic, irregular or bizarre nuclei (monster cells, Am J Dermatopathol 1987;9:380) and foamy or hemosiderin-rich cytoplasm
      • Mild to marked pleomorphism
      • Cellular variant: highly cellular and extends into subcutaneous fat
      • Clear cell: contains mainly clear cells
      • Cholesterotic
      • Epithelioid variant: > 50% of cells exhibit polygonal or rounded appearance with abundant eosinophilic cytoplasm
      • Hemosiderotic
      • Lipidized "ankle type"
      • Myxoid: myxoid changes
      • Palisading: nuclear palisading
  • Changes may involve both the architectural and cellular / stromal appearances
Microscopic (histologic) images

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AFIP images
Tumor is more basophilic than surrounding dermis

Tumor is more basophilic than surrounding dermis

Increased cellularity

Increased cellularity

Sharp border

Sharp border

Histiocyte-like and foam cells

Histiocyte-like and foam cells

Mostly fibrous tumor cells

Mostly fibrous tumor cells

Fat may be entrapped at edge

Fat may be entrapped at edge


Foam cells, fibroblasts and histiocyte-like cells

Foam cells, fibroblasts and histiocyte-like cells

Foam cells and cholesterol clefts

Foam cells and cholesterol clefts

Enlarged cells Enlarged cells Enlarged cells

Enlarged cells



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Tumor with hyperplastic epithelium Tumor with hyperplastic epithelium

Tumor with hyperplastic epithelium

Hyperplastic epidermis and sclerotic stroma Hyperplastic epidermis and sclerotic stroma Hyperplastic epidermis and sclerotic stroma

Hyperplastic epidermis and sclerotic stroma

Foam cells with vacuolated cytoplasm

Foam cells with vacuolated cytoplasm


Fibroblastic cells<br>with vacuolated<br>cytoplasm in<br>collagenous stroma

Fibroblastic cells
with vacuolated
cytoplasm in
collagenous stroma

Spindle cell nodule

Spindle cell nodule

Paucicellular dermal tumor

Paucicellular dermal tumor

Spindle cells in dense collagenous stroma

Spindle cells in dense collagenous stroma

Various images Various images

Various images


H&E and D2-40

H&E and D2-40

Virtual slides

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Lump on back

Lump on back

Excision biopsy of pigmented lesion right lower thigh

Excision biopsy of pigmented lesion right lower thigh

Cystic lesion from forearm sarcoma

Cystic lesion from forearm sarcoma

Skin of left upper arm

Skin of left upper arm

Skin of back of neck

Skin of back of neck

Positive stains
  • Note that BFH has a highly variable immunohistochemical profile
  • Factor XIIIa is expressed by the tumor dendritic cells but is not specific / diagnostic
  • Myoid markers may be weakly expressed (SMA and smooth muscle myosin)
Negative stains
  • CD34 is used to differentiate between BFH (CD34-) and dermatofibrosarcoma protuberance (CD34+)
    • However, a thin rim of CD34 positivity can be seen at the periphery of BFH lesions
    • CD34 and factor XIIIa may be difficult to interpret because of background entrapped reactive cells
  • Apolipoprotein D is negative
Molecular / cytogenetics description
  • Often clonal
Videos

Diagnosis and Treatment

Differential diagnosis
Board review style question #1
How can you differentiate between dermatofibroma and dermatofibrosarcoma protuberans with immunohistochemistry?

  1. Cannot - both are diffusely positive for CD34
  2. Cannot - both are negative for CD34
  3. Dermatofibrosarcoma protuberans is strongly, diffusely positive for CD34 but dermatofibroma / variants are otherwise negative / weakly positive / showing peripheral rim of positivity for CD34
  4. Dermatofibrosarcoma protuberans is completely negative for CD34 and dermatofibroma is strongly positive for CD34
Board review answer #1
C. Dermatofibrosarcoma protuberans is strongly, diffusely positive for CD34 but dermatofibroma / variants are otherwise negative / weakly positive / showing peripheral rim of positivity for CD34
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