Dermatofibrosarcoma Protuberans of the Clavicular Skin in a 70-Year-Old Woman: Case Report and Management.

Dermatofibrosarcoma protuberans (DFSP) is a rare, low-grade soft tissue sarcoma. It typically arises in younger to middle-aged adults, while patient age ≥60 years and larger tumor sizes are associated with worse overall and cancer-specific survival. We present the case of a 70-year-old woman with a one-year history of a progressively enlarging, tender erythematous plaque on the left clavicle. Differential diagnosis included dermatofibroma, DFSP, leiomyoma, cutaneous leiomyosarcoma, cutaneous lymphoma, and leukemia cutis. Punch biopsy revealed a CD34-positive spindle cell neoplasm, and fluorescence in situ hybridization confirmed COL1A1 rearrangement, consistent with DFSP. The patient underwent Mohs micrographic surgery, with clear margins achieved after two stages. This case highlights an atypical age of presentation and reinforces the importance of early biopsy and molecular confirmation for accurate diagnosis. Mohs micrographic surgery remains the preferred treatment, offering precise tumor margin control and minimizing recurrence risk compared to wide local excision, while systemic options such as imatinib are reserved for unresectable or metastatic disease. Early recognition and intervention are especially critical in older patients, given their higher risk of adverse outcomes.