Parosteal osteosarcoma of the mastoid bone following radiotherapy for nasopharyngeal carcinoma.

Radiation-induced tumors subsequent to nasopharyngeal carcinoma are very rare. To date, no post-irradiation parosteal osteosarcoma of the craniofacial bone has been reported in the English literature. In October 2000, a 57-year-old Chinese woman presented 5 years after radiotherapy for nasopharyngeal carcinoma with a 6-month history of a gradually enlarging left postauricular mass. CT scans revealed a densely calcified mass with radiating bony spicules, applied to left mastoid tip. The lesion was excised en-bloc through a postauricular incision. The histologic diagnosis was a parosteal osteosarcoma. Because of inadequate safe margins and the patient refusal of another surgery, 6600 cGy of radiation was subsequently administered to the temporal bone. Post-operative follow-up in 3 years was negative for any evidence of tumor recurrence and post-irradiation complications.