Primary intraosseous carcinoma of the mandible with probable origin in an odontogenic cyst.

Primary intraosseous carcinoma of the jaws (PIOC) is an uncommon lesion, but may not be as rare as commonly believed. Since the putative source of the epithelium giving rise to an intraosseous carcinoma is the epithelium involved in odontogenesis, these lesions are often designated as odontogenic carcinomas. These tumors may theoretically arise (1) from the lining of odontogenic cysts, (2) from other epithelial odontogenic tumors, or (3) de novo from presumed odontogenic rests. While not included in most classifications of PIOC, it appears logical to also include intraosseous mucoepidermoid carcinomas as a fourth type of PIOC. A case of primary intraosseous squamous cell carcinoma of the mandible, with evidence of origin in an odontogenic cyst, is presented. The recent literature on carcinomas arising in jaw cysts is reviewed.