DFSP

Dermatofibrosarcoma protuberans (DFSP) is a rare, slow-growing malignant skin tumor classified as a soft tissue sarcoma. It is locally aggressive with a high risk of local recurrence after treatment but a low probability of distant metastasis.

DFSP arises from dermal fibroblasts and typically infiltrates into the subcutaneous tissue. It is characterized histologically by a storiform (spindle cell) pattern and CD34 positivity; a defining molecular feature is the COL1A1-PDGFB gene fusion resulting from a chromosomal translocation t(17;22), which drives tumor growth through PDGFR signaling.

Clinically, DFSP presents as a firm, slowly enlarging plaque or nodular lesion on the trunk or proximal limbs, often with a reddish-brown appearance. It may be asymptomatic at first, progressing to protuberant masses over months to years. It can occur at any age but commonly affects adults.

Diagnosis involves biopsy with histopathology and immunohistochemistry. Imaging such as MRI helps assess deep invasion. Molecular testing or fluorescence in situ hybridization can confirm COL1A1-PDGFB fusion.

Treatment relies on complete surgical excision with wide margins; Mohs micrographic surgery has high cure rates and tissue-sparing benefits. Standard excision margins of 2-5 cm may be used. Radiotherapy may be considered when surgery is not feasible or margins are positive. For unresectable, recurrent, or metastatic DFSP with COL1A1-PDGFB fusion, targeted therapy with imatinib can be effective.

Prognosis is generally favorable with appropriate treatment, but the risk of local recurrence remains substantial, potentially requiring long-term follow-up. Metastasis is uncommon.

DFSP is rare, with an estimated incidence of about 0.8-5 cases per million people per year. It was first described in the 1920s by Darier and Ferrand and has since become the most common type of cutaneous sarcoma.