Soft tissue
Fibrohistiocytic tumors
Benign fibrous histiocytoma (superficial)

Author: Engy Abdellatif M.B.B.Ch., Ph.D., M.D. (see Authors page)

Editorial Board Review: Lauren N. Stuart, M.D., M.B.A.

Revised: 2 August 2017, last major update June 2017

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Benign fibrous histiocytoma [title]

Cite this page: Benign fibrous histiocytoma (superficial). PathologyOutlines.com website. http://pathologyoutlines.com/topic/softtissuebfh.html. Accessed August 22nd, 2017.
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
Images hosted on other servers:

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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Images hosted on PathOut servers:

Breast skin, courtesy of Mark R. Wick, M.D.

Courtesy of Mark R. Wick, M.D.



Images hosted on other servers:

Dermatofibroma on the skin


Dimpling when squeezed along margins

Dermatofibroma on the right upper back

A very flat dermatofibroma


Dermatofibroma on the arm

Side on view

Dermatofibroma on the waist

Cellular dermatofibroma



Dermoscopy images:

A central scar-like area associated with a peripheral pigment network


Pseudonetwork present

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

Dermoscopic appearance and close up

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
Images hosted on other servers:

Ulcerated cutaneous mas

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:
      • 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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Images hosted on PathOut servers:

Tumor is more basophilic than surrounding dermis

Basophilia is due to increased cellularity

Sharp border between tumor and subcutis

Tumor cells are
composed of
histiocyte-like cells
and foam cells

Tumor cells are mostly fibrous in this focus


Fat may be entrapped
at edge but must
differentiate from
infiltration of DFSP

       

Randomly arranged foam cells,
fibroblasts and histiocyte-like
cells; foam cells are somewhat
specific for this lesion

       

Less common finding
of predominately
foam cells and
cholesterol clefts



Images courtesy of Mark R. Wick, M.D.:

Breast skin

Aneurysmal type

Cellular type

Deep penetrating



Granular cell change


Palisading type

Sclertoic type

Nuclear pleomorphism



Images hosted on other servers:

Tumor with hyperplastic epithelium

Hyperplastic epidermis and sclerotic stroma


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


Various images

H&E and D2-40

Virtual slides
Images hosted on other servers:

Lump on back

Excision biopsy of pigmented lesion right lower thigh

Cystic lesion from forearm Sarcoma

Skin of left upper arm

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 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