The canine furcation cyst, a newly defined odontogenic cyst in dogs: 20 cases (2013-2017).

To characterize clinical, radiographic, and histologic features of canine furcation cysts (CFCs) in dogs and to propose possible mechanisms of CFC development. 20 client-owned dogs with CFCs biopsied between January 1, 2013, and December 31, 2017. Medical records of the Center for Comparative Oral and Maxillofacial Pathology at the University of Wisconsin-Madison were retrospectively searched to identify records of dogs that had surgical biopsy specimens of mandibular or maxillary cavitary lesions diagnosed as odontogenic cysts and that met additional inclusion criteria. Biopsy sample submission records, medical records, clinical and radiographic images, and histologic samples were reviewed. Clinical, radiographic, and histologic features were evaluated. Mean body weight and age of affected dogs were 23.5 kg (51.7 lb) and 8.2 years, respectively. All 20 dogs had a unilateral cyst, with the right (n = 13) or left (7) maxillary fourth premolar tooth affected and viable in all dogs. A predominant clinical sign was a fluctuant swelling of the buccal gingiva and mucosa overlying the CFC, and enucleation of the cyst lining, with or without extraction of the affected tooth, resolved the lesion in most dogs. Our findings indicated that CFC is an odontogenic cyst of uncertain etiopathogenesis and that complete evaluation of the clinical, radiographic, and histologic features of the lesion in affected patients is necessary to distinguish a CFC from other odontogenic cysts and tumors in dogs. Defining CFCs in terms of characteristic features permits accurate diagnosis and appropriate treatment of these previously unclassifiable odontogenic cysts in dogs.