Squamous-cell carcinoma arising from an odontogenic cyst--the importance of computed tomography in the diagnosis of malignancy.

Primary intraosseous carcinoma of the mandible is rare, and when it occurs often arises within or closely associated with an odontogenic cyst. The purpose of this article is to show the role of computed tomography (CT) in the early detection of carcinomatous changes, because of its specificity in establishing the nature of the lesion. An unusual case of a squamous cell carcinoma that arose in an odontogenic cyst is described. The appearance on the panoramic radiograph was suggestive of a benign cystic lesion in the left side of the mandible, but when a CT scan was performed, the appearance of the lesion was compatible with malignancy. Histopathological analysis confirmed the suspicion of a squamous cell carcinoma, but without CT investigation it would be impossible to demonstrate that carcinomatous change had developed from a cystic lesion.