Radiation-induced malignant fibrous histiocytoma in patients with nasopharyngeal carcinoma

Objective: To evaluate the prevalence, 15-year cumulative incidence, time interval, and prognosis of radiation-induced malignant fibrous histiocytoma of the head and neck in long-term survivors of nasopharyngeal carcinoma. Design: Cohort. Setting: Tertiary care hospital. Patients: Eight long-term survivors of nasopharyngeal carcinoma with malignant fibrous histiocytoma in the maxillary sinus or nasal cavity. Main Outcome Measurement: Survival of postirradiation malignant fibrous histiocytoma in patients with nasopharyngeal carcinoma. Results: The prevalence of radiation-induced malignant fibrous histiocytoma in long-term survivors of nasopharyngeal carcinoma was 0.38%. The 15-year cumulative incidence was 2.2%. Most tumors occurred in the maxillary sinus and were characterized by spindle-shaped tumor cells with plump nuclei arranged in a whorl or storiform pattern in a fibrous stroma. The mean interval between malignant fibrous histiocytoma and nasopharyngeal carcinoma was 121 months. Local recurrence developed in all cases within 9 months after surgery. Six patients died of disease without distant metastasis within 30 months. Two patients were alive with disease for 10 and 32 months, respectively. Conclusions: Radiation-induced malignant fibrous histiocytoma in the head and neck region in long-term survivors of nasopharyngeal carcinoma is rare. It takes a long time to occur after irradiation and is locally invasive with poor prognosis.