A case of exostosis at the inferior border of the mandible

A case of exostosis at the inferior border of the mandible was reported. The patient was a 66-year-old woman who complained chiefly of painless swelling at the inferior border of the left mandible. Physical examination disclosed a firm and hard mass, adhering to the inferior surface of the mandible. Roentogenograms of the mandible disclosed a cylindric, radiopaque appearance, which extended outward beyond the normal inferior border of the left mandible. The clinical diagnosis was exostosis. Surgical removal of the bony mass was done under local anestl-esia. The bony mass was about 6 mm in diameter and 12 mm in length. Its histopathological diagnosis was also exostosis. Generally, exostosis is not a rare disease, but such cylinder shaped exostosis occurring at the inferior border of the mandible as seen in this case was extremely rare. And we could not find out the cause of the lesion in this case.The patient was last seen about two years after the operation and no evidence of further trouble was found clinically and roentogenologically at that time.