Dermatofibromas are common benign dermal proliferations, often presenting as firm papules or nodules on the extremities of young to middle-aged adults. They are usually asymptomatic but may be pruritic or tender. The characteristic clinical sign is a central “dimple” on lateral compression. Variants include aneurysmal, cellular, and atrophic forms, which can mimic malignant tumors. Diagnosis is clinical aided by dermoscopy; excision is reserved for diagnostic uncertainty, symptoms, cosmetic reasons, or atypical variants.
Epidemiology and Risk Factors
- More frequent in women; commonly appear on lower legs.
- Often arise at sites of minor trauma/insect bites; pathogenesis involves fibroblast/myofibroblast proliferation.
Clinical Features
- Firm, 0.5–1.5 cm papule/nodule, tan to brown, sometimes pink; surface may be smooth or slightly scaly.
- Dimple sign: lesion depresses centrally with lateral pressure due to tethering to the dermis.
- Common on lower extremities; multiple lesions possible.
- Pigmentation more prominent in darker skin; may show peripheral ring of hyperpigmentation.
Differential Diagnosis
- Epidermal inclusion cyst, intradermal nevus, keloid/hypertrophic scar, leiomyoma, neurofibroma, Spitz nevus/melanoma (especially pigmented and changing lesions), dermatofibrosarcoma protuberans (DFSP) for larger plaque-like lesions, Kaposi sarcoma (vascular variant mimic).
- Aneurysmal and cellular variants can mimic melanoma or sarcoma clinically and histologically.
Dermoscopy
- Central white scar-like area with peripheral delicate pigment network; dotted/glomerular vessels may be present.
- Variants have diverse patterns; lack of melanoma-specific structures supports benignity but is not definitive.
Diagnosis
- Clinical and dermoscopic in typical cases.
- Biopsy/excision indicated for:
- Rapid growth, ulceration, atypical pigmentation, size >2 cm, symptomatic lesions, or uncertainty with melanoma/DFSP.
- Histology: storiform proliferation of spindle cells in dermis with collagen entrapment; epidermal hyperplasia; factor XIIIa positive, CD34 negative (helps distinguish from DFSP, which is CD34 positive, FXIIIa negative).
Management
- Reassurance if typical.
- Symptomatic or cosmetic removal: tangential shave may leave residual; full-thickness excision with narrow margins for definitive removal (scarring risk).
- Recurrence rare but possible, especially with partial removal; cellular/aneurysmal variants have higher recurrence—consider wider excision.
Special Considerations
- Atrophic dermatofibroma: depressed center; can mimic anetoderma or scar.
- Multiple eruptive dermatofibromas: may associate with immunosuppression or autoimmune disease—evaluate if numerous and rapidly appearing.
References (recent guidelines and reviews)
- Dermoscopic criteria and pitfalls for dermatofibroma, 2021–2024.
- Pathologic differentiation from DFSP and atypical variants, 2021–2024.