Carcinoma arising from reduced enamel epithelium.

Intra-osseous squamous cell carcinomas are considered to be derived from odontogenic epithelium. Except for an associated benign odontogenic tumor or a cyst, evidence for an odontogenic origin is only circumstantial. In a 73-year-old male, an intra-osseous squamous cell carcinoma in the mandible could be shown to have originated from reduced enamel epithelium. There were no histological features substantiating the odontogenic origin, other than the continuity of tumor epithelium with reduced enamel epithelium surrounding the crown of an impacted molar tooth. Thus, it is concluded that the odontogenic derivation of an intra-osseous squamous cell carcinoma in the jaw cannot be inferred from specific histological features, but should be based on the exclusion of an oral cavity lining epithelial origin. Still more proof is the demonstration of continuity of the carcinoma with odontogenic epithelium, be it normal, cyst lining or benign odontogenic tumor.