Mandibular lesion differential diagnoses in a patient with a previous history of locally advanced head and neck carcinoma.

Eighteen months after completion of radiochemotherapy treatment for a T4 squamous cell tonsil carcinoma, the patient presented with a piece of bone coming out through a submandibular fistula and had increasing pain. Several imaging modalities were used to investigate this lesion. The CT scan, orthopantomogram, and bone scintigraphy suggested osteonecrosis, whereas the F-18 FDG PET scan showed tumor recurrence. Finally, both diagnoses of osteoradionecrosis and tumor recurrence were confirmed after mandibulectomy, performed because of a mandibular pathologic fracture.