Immunohistochemical analysis of a dentigerous cyst in a dog.

A dentigerous cyst is a cyst that encloses part or the entire crown of an impacted or late-erupting tooth and occurs with comparatively high frequency in humans. In animals, there are three different lesions that are similar to dentigerous cyst and this complexity has led to confusion. In order to clarify the dentigerous cyst most similar to that in humans especially with regard to characteristics of the lining epithelium, this report describes the clinical, pathological, and immunohistochemical features of a dentigerous cyst in a dog. Further, approaches to the surgical and dental management of this cyst in dogs are also discussed and the literature is reviewed. Extraction of an embedded right mandibular first premolar tooth and debridement of the dentigerous cyst soft tissue lining were performed in a 4-year-old female mixed-breed dog. Radiography showed a well-defined unilocular and radiolucent area associated with the crown of the unerupted tooth. Histologically, the unilocular cyst wall was mainly lined by non-keratinized stratified flattened epithelium. As in humans, canine dentigerous cyst can be appropriately treated by cyst enucleation after accurate diagnosis. The radiographic appearance of an unerupted tooth embedded in an osseous cyst wall is a significant characteristic finding. Moreover non-keratinized epithelium is immunoreactive for amelogenin and ssDNA, which might be associated with deregulation of cell death in the lining epithelium, derived from odontogenic origin. When encountering any questionable lesions, an accurate diagnosis and immediate treatment can avoid malignant transformation.