Maxillary ameloblastic fibroma in a dog.

A 4-year-old spayed female Golden Retriever was presented for evaluation of a rostral maxillary gingival mass. An en bloc resection was performed after histologic diagnosis of ameloblastic fibroma from an incisional biopsy specimen. Histologically, the tumor was composed of (1) poorly differentiated vimentin-positive mesenchymal cells that surrounded islands and (2) thin anastomosing trabeculae of odontogenic epithelium that variably coexpressed pancytokeratin and vimentin. To the authors' knowledge, this is the first report of ameloblastic fibroma in a dog. The clinical, radiographic, and histologic findings in this case are compared to those in other domestic animals and humans.