The relationship of the canine acanthomatous epulis to ameloblastoma

This paper compares the microscopic features and clinical behaviour of the acanthomatous epulis in dogs with those of ameloblastoma in human beings. The acanthomatous epulis has similar microscopic features to one histological variant of human ameloblastoma, the acanthomatous ameloblastoma. Moreover, its clinical behaviour is equivalent to that of intraosseous ameloblastoma in human beings, not of the human peripheral (extraosseous) ameloblastoma, as has been suggested. The stroma of acanthomatous epulides varies and does not always resemble periodontal ligament, a feature that in dogs has been used to distinguish them from ameloblastomas. It is concluded that the acanthomatous epulis (1) is an ameloblastoma, (2) arises from the gingival epithelium in some cases, but (3) may also arise intraosseously and then break out of bone. We recommend the term canine acanthomatous ameloblastoma as being appropriate for this lesion.