Recommendation of modified classification for odontogenic carcinomas.

Primary squamous cell carcinoma (SCC) derived from odontogenic epithelium is diagnosed as primary intraosseous carcinoma (PIOC). The term "intraosseous" means the bone marrow spaces. Odontogenic cells, however, exist not only in the bone marrow space but also in the periodontal space and the subepithelial soft tissue space. In our survey for 36 SCC lesions of odontogenic origin, many lesions involved two or all of the three spaces. There was only one lesion which involved the bone marrow space alone. In some cases, the extent of the early lesions was restricted around the tooth or at a part of the alveolar crest. The possibility of a SCC of odontogenic origin arising in the periodontal and the subepithelial soft tissue spaces was suggested. We proposed the term "Odontogenic SCC" to replace "PIOC".