Radiation‐induced osteosarcoma involving the mandible – report of a rare diagnosis

Background Radiation-induced osteosarcomas of the jaws are a rare but often fatal consequence of radiation therapy in the head and neck region. Here we present a case of radiation-induced osteosarcoma of the mandible. Case Presentation A male presented with severe trismus and marked left lingual alveolus expansion 1 year following extractions in the lower left quadrant. Four years previously, he had radical radiotherapy (70Gy) and chemotherapy for a p16-positive T1N2cM0 squamous cell carcinoma of the left tonsil with a positive left level II node. Initial bone biopsies of the left mandible showed a bony sequestrum suggestive of osteoradionecrosis with the presence of abnormal osteoid suspicious of osteosarcoma. Imaging demonstrated an abnormal exophytic bone-forming lesion in the left mandibular body and parasymphysis and ruled out a metastatic lesion. The patient underwent bilateral neck dissection, left mandibulectomy with fibula flap reconstruction and full-thickness skin graft. Conclusions Osteosarcoma should be considered if changes are seen in previously stable irradiated bone with bony destruction and a soft tissue mass. This case highlights the importance of synthesis of clinical, radiological and pathological findings in the diagnosis of such lesions, especially where the histology initially suggested a benign process