Dermatofibrosarcoma protuberans

Clinical features

DFSP typically presents as a slow-growing, indurated, violaceous plaque, often misdiagnosed as a keloid or dermatofibroma for years before nodular transformation. Most cases arise on the trunk (40–50%), proximal extremities, or head and neck in young to middle-aged adults.

Diagnosis

Incisional biopsy essential — shave biopsies underestimate depth. Histology shows a storiform dermal spindle cell proliferation infiltrating subcutaneous fat in a honeycomb pattern with uniform CD34 positivity. Factor XIIIa is negative, contrasting with dermatofibroma.

Molecular confirmation of COL1A1-PDGFB fusion recommended for atypical cases and prior to imatinib.

Management

Surgery

• Mohs or slow (staged) Mohs with CD34 IHC is the preferred technique where available — lower recurrence and tissue-sparing; histologically clear is the standard.
• Where Mohs is not available: wide local excision with 2 cm peripheral margin (range 1–3 cm) to and including muscle fascia, with delayed reconstruction pending paraffin margin clearance.
• Reconstruction often requires local flaps, regional flaps (e.g. keystone) or free tissue transfer.

Adjuvant therapy

• Adjuvant radiotherapy for positive margins where re-excision is not feasible.
• Imatinib 400–800 mg/day for unresectable or metastatic disease, or as neoadjuvant cytoreduction.

Follow-up

• Primary DFSP, completely resected and without high-risk pathology: clinical examination focused on the primary site every 6 months for the first 3 years, then annually in years 4–5.
• Higher-risk DFSP (recurrent tumour, narrow margins, fibrosarcomatous transformation or difficult local assessment): clinical review every 6 months for 2 years, every 6–12 months in years 3–5, then at least annually in years 6–10.
• Ultrasound or MRI if recurrence is suspected, or as part of high-risk local assessment after MDT discussion.
• CT chest for DFSP-FS — metastasis is uncommon in conventional DFSP but, when it occurs, is usually pulmonary.