Double malignant neoplasms occurring long after local radiation to the oral mucosa.

A 59-year-old woman who had received cobalt-60 (60Co) interstitial radiation therapy (total 44 Gy) in the right bucco-gingival region for inflammatory pseudotumour was found to have metachronous double malignant neoplasms. Initial osteosarcoma of the right mandibular angle and subsequent squamous cell carcinoma of the right buccal mucosa were identified 28 and 33 years after the radiation, respectively. Since both tumours were located very close to the focus of previous radiation, the therapy was considered to be responsible for their genesis. The patient had systemic metastases of the osteosarcoma.