Radiotherapy induced soft tissue sarcoma: an unusual case of a dermatofibrosarcoma protuberans.

We report a patient with unusual high grade dermatofibrosarcoma protuberans, confirmed by immunohistochemistry, which developed at radiotherapy field margins 5.7 years after radiotherapy for a squamous cell glottic cancer. The sarcoma relapsed locally after inadequate excision and developed lung metastases, as confirmed by fine needle aspiration. Radiotherapy induced soft tissue sarcomas may differ histologically from their spontaneous counterparts. Even a low radiation dose at the field margins can induce a soft tissue sarcoma.