Pathology of Fibrous Histiocytoma (Dermatofibroma)

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Dr Sampurna Roy MD 2022

This is a common dermal tumour which usually occurs on the extremities in young adults.

Fibrous histiocytoma is regarded as a neoplastic lesion by some authors and an inflammatory or reactive process by others.

Gross: These are usually solitary round or ovoid firm nodule, less than 1cm in diameter.

Aneurysmal variant may be upto 10 cms in diameter. Dark brown or red in colour.

Cream or yellowish cut surface is noted in tumour with abundant lipid.

Microscopic features:

- Symmetric lesion in the dermis.

- Epidermal hyperplasia is usually present.

- Grenz zone is noted in almost 70% cases.

- Rarely extend into superficial subcutis (as a well defined bulge or septal extension).

- Storiform growth pattern.

- Mixed population of cells (fibrocytic, histiocytic or mixed).

- Hyalinized collagen fibers surrounded by spindle cells at the periphery - (keloidal pattern)

- Birefringence of intralesional collagen with polarization present .

Various changes may be present in the overlying epidermis:

- Acanthosis with basal hyperpigmentation;

- Seborrheic keratosis like pattern;

- Epidermal atrophy;

- Intraepidermal carcinoma;

- Basaloid hyperplasia with rudimentary pilar structure (difficult to distinguish from basal cell carcinoma) ;

- Sebaceous structures

Further reading: Anti-cytokeratin 20 staining of Merkel cells helps differentiate basaloid proliferations overlying dermatofibromas from basal cell carcinoma.

Follicular basal cell hyperplasia overlying dermatofibroma.

Sebaceous hyperplasia: a clue to the diagnosis of dermatofibroma.

Plate-like sebaceous hyperplasia overlying dermatofibroma.

Proliferation and differentiation of the keratinocytes in hyperplastic epidermis overlying dermatofibroma: immunohistochemical characterization.

Dermatofibroma may be associated with melanocytic lesions.

Melanocytic lesions associated with dermatofibromas: a spectrum of lesions ranging from junctional nevus to malignant melanoma in situ.

Dermatofibroma may occur in patients associated with HIV infection.

Multiple eruptive dermatofibromas in three men with HIV infection.

Presence of Leishmania organisms in specific and non-specific skin lesions in HIV-infected individuals with visceral leishmaniasis.

Immunohistochemistry

CD34: (-) or (+/-)

Factor XIIIa: (+)

S100: (-) or (-/+)

HMB45: (-)

HAM56: (+)

HHF-35: (+) to (+/-)

Smooth muscle actin : (+/-)

Desmin: (+/-)

Cytokeratin: (-)

Variants of Dermatofibroma:

Read the article: Alves JVP, Matos DM, Barreiros HF, Bártolo EAFLF. Variants of dermatofibroma - a histopathological study . Anais Brasileiros de Dermatologia. 2014;89(3):472-477. doi:10.1590/abd1806-4841.20142629.

- Fibrocollagenous : Mainly collagen and fibroblast like cells in irregular or whorled pattern.

- Storiform: Prominent storiform pattern. These are often termed fibrous histiocytoma.

- Lipidized : Presence of numerous foam cells.

Further reading: Lipidized fibrous histiocytoma: clinicopathologic analysis of 22 cases.

- Angiomatous: Presence of small branching vessels in a collagenous stroma. Hemosiderin may be present.

- Aneurysmal Variant: Visit: Dermatofibroma (aneurysmal variant)

- Clear Cell:

Differential Diagnosis: Metastatic renal cell carcinoma, xanthogranulomatous reactions, balloon cell naevus / melanoma and clear cell sarcoma.

Further reading: Clear cell dermatofibroma ;

Clear cell dermatofibroma. Case report of an unusual fibrohistiocytic lesion.

- Cholesterotic associated with hyperlipoproteinemia: Cholesterotic fibrous histiocytoma. Its association with hyperlipoproteinemia.

- Granular cell:

Further reading: Granular cell dermatofibroma;

Granular cell dermatofibroma;

Dermatofibroma with granular cells: a report of two cases.

- Monster cell:

Atypical bizarre cells with foamy cytoplasm, hyperchromatic nuclei.

Further reading: Giant dermatofibroma with monster cells.

Dermatofibroma with monster cells.

Further reading: Case of dermatofibroma with monster cells: a review and an immunohistochemical study.

- With Osteoclast - like Giant Cells:

Further reading: Dermatofibroma with osteoclast-like giant cells.

- Ossifying:

Further reading: Ossifying dermatofibroma with osteoclast-like giant cells.

- Myofibroblastic:

Further reading: Prominent myofibroblastic differentiation. A pitfall in the diagnosis of dermatofibroma.

- Myxoid: Stromal mucin is present. (Differential diagnosis: Cutaneous myxoma).

Further reading: Myxoid dermatofibroma on a great toe: a case report.

Myxoid dermatofibroma.

Decreased CD44 expression and stromal hyaluronate accumulation in myxoid dermatofibroma.

- With smooth muscle: Smooth-muscle proliferation in dermatofibromas.

- Keloidal : Keloidal dermatofibroma: report of 10 cases of a new variant.

- Palisading:

Further reading: Palisading subcutaneous fibrous histiocytoma.

Palisading cutaneous fibrous histiocytoma. An immunohistochemical study demonstrating differentiation from dermal dendrocytes.

- Atrophic :

Further reading: The atrophic dermatofibroma: a delled dermatofibroma.

Atrophic dermatofibroma. Elastophagocytosis by the tumor cells.

Differential diagnosis : Atrophic variants of dermatofibroma and dermatofibrosarcoma protuberans.

- Subcutaneous :

Further reading: Dermatofibroma extending into the subcutaneous tissue. Differential diagnosis from dermatofibrosarcoma protuberans.

- Combined :