[Extra-abdominal desmoid tumor--report of a case].

A case of an extra-abdominal desmoid tumor in a 17-year-old female is reported. At the time of the first examination, the tumor was found to already involve the floor of the mouth, the submandibular region, both sides of the neck, the anterior chest wall and the mediastinum and hence was considered inoperable. The patient was treated by external irradiation and interstitial irradiation (Ir and Au). The therapeutic response was very slow, becoming noticeable 4 months after completion of the therapy and lasting for more than a year. Experience in this case indicates that in order for radiotherapy to prove successful in the treatment of desmoid tumor, it must be administered in relatively high doses. Since desmoid tumors reportedly have the potential for sarcomatous transformation, a long-term follow-up seems to be necessary in the management of patients with this neoplasm. It is considered that inoperable extra-abdominal desmoid tumors are a good indication for radiation therapy.