PubMed · 5250321
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J Snijder, J Leeuwenburgh. 1969. [The calcifying dentogenic cyst].. https://pubmed.ncbi.nlm.nih.gov/5250321/
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In this paper odontogenic tumours in animals are discussed with the aim of developing a sound basis for further work in this relatively poorly understood field. The following recommendations are made: (1) Odontogenic tumours should be classified according to whether they are of epithelial, mesenchymal or of mixed epithelial and mesenchymal origin, rather than based on inductive changes. (2) The clinical behaviour implied by ameloblastoma, ameloblastic fibroma and odontoma should be carefully considered before these terms are incorporated into the diagnosis of any odontogenic tumour. (3) Caution should be exercised in designating specific odontogenic tumours in animals as being the counterpart of human tumours until their histopathological features and clinical behaviour have been proved to be equivalent. (4) Only tumours that exhibit the typical features of the basal cell layer of ameloblastomas should be designated as ameloblastomas. (5) Ameloblastic epithelium should not be used when odontogenic epithelium is intended. (6) These recommendations should be substantiated by reviewing odontogenic tumours in animals, although doing so will be difficult because of their rarity.
The histological characteristics of a series of 154 oral tumours with the clinical appearance of epulides in 129 dogs were reviewed. Diagnoses were based on current criteria in human oral pathology and compared with the original diagnoses. The histological findings suggested that the majority of epulides in the dog can be classified as focal fibrous hyperplasia (43.5 per cent), peripheral ameloblastoma (17.5 per cent), peripheral odontogenic fibroma (WHO type) (16.9 per cent) and pyogenic granuloma (1.95 per cent). In addition, a number of other odontogenic tumours (1.95 per cent) and non-odontogenic tumours (18.2 per cent) such as fibrosarcoma and squamous cell carcinoma, which are not traditionally associated with the clinical appearance of an epulis, were diagnosed. Of 74 lesions that were previously diagnosed as fibromatous and ossifying epulides, 50 (68 per cent) were reclassified as focal fibrous hyperplasia and 21 (28 per cent) as peripheral odontogenic fibroma (WHO type). The majority of lesions (76 per cent), which were originally classified as acanthomatous epulis, were found to be peripheral ameloblastoma. In addition, three squamous cell carcinomas, two rare odontogenic tumours and two cases of focal fibrous hyperplasia were diagnosed in this classification. It was concluded that, as in man, the term epulis is a clinically descriptive term and that the renal nature of these lesions should be determined histologically.
Instructive signals are responsible for the regulation of the expression of gene products characteristic of many cell lineages during normal development and potentially during neoplasia. The odontogenic origin of ameloblastomas is based largely on the similarity in histologic appearance between the tumor and the developing tooth organ. A pathognomonic pattern for odontogenic tissue-specific gene expression in ameloblastomas has not been previously shown. In these studies, the gene expression parameters for human ameloblastomas have been characterized with the techniques of messenger RNA phenotyping in combination with Northern and in situ hybridization analysis of messenger RNA. The results of these studies confirm that amelogenin, a gene transcribed solely by differentiated ameloblasts, was expressed by epithelial cells from human ameloblastomas. This observation suggests that the instructive signals required for ameloblast differentiation are shared during normal development and tumorigenesis of odontogenic epithelium.