[Classification of epithelial odontogenic tumors]

A retrospective series of 31 purely epithelial odontogenic tumours consisted of 21 ameloblastomas, 2 adenomatoid odontogenic tumours, 2 calcifying epithelial odontogenic tumours, and 6 calcifying odontogenic cysts. Modern histological classification gives an accurate picture of some of the structural and biological differences between the above types of tumour. In spite of the, their common basis does result in some of the common features so that the precise classification of the specific tumour may pose problems or give rise to terminological disputes. For practical work it will do in the group of epithelial odontogenic tumours to insist strictly on the basic condition of the absence of either proliferating mesenchyma or hard dental tissues. This requirement naturally leads to the placing of ameloblastic odontoma outside the field of purely epithelial odontongenic tumours. Judging the biological nature of epithelial odontogenic tumours according to their structure is not reliable, a fact brought out by comparisons of ameloblastoma and adenomatoid odontogenic tumours. Rather one could rely on the nature of tumour growth. An evidently carcindependent classification pattern. Suspicion of a higher degree of malignity can be expressed by description.

[Classification of mesenchymal odontogenic tumors]

A retrospective series of 9 purely mesenchymal odontogenic tumours was found to consist of 3 odontogenic fibromas, 2 myxomas, and 4 cementomas including one true benign cementoblastoma and two cementifying fibromas. One as seen to contain a conspicuously blood supplied proliferating fibrous component giving the tumour the appearance of a malignant process though no relapse was noted after the jaw resection. Periapical cement dysplasia was seen in only one case of the group; there was no case of gigantiform cementoma. The problems of mutual differential diagnosis and distinction from osteogenic tumours are subject to discussion.

[Classification of epitheliomesenchymal odontogenic tumors]

In a group of 34 epitheliomesenchymal odontogenic tumours no difficulties were encountered in recognizing the seven-member group of ameloblastic fibroma (with ameloblastic odontoma and dentinoma included as variants) as distinct from group of odontomas (ameloblastic o. - 2x, complex o. - 20x, combined o. - 5x) The definition is rather a general one with the distinction of variants only sometimes possible. No ameloblastic fibrosarcoma or ameloblastic odontosarcoma were seen in the group; therefore, the question should be asked whether it is really expedient to keep independent places in the classification for so rare tumours.