History and Physical Examination FindingsA 2-year-old 32-kg (70.5 lb) spayed female mixed-breed dog was referred to the Animal Hospital of Verona for evaluation of a cystic lesion of the oral cavity. Previous examination had not yielded a definitive diagnosis.Oral examination revealed a purple to pink swelling approximately 15 X 20 X 11 mm involving the dorsal aspect of the left hemi-mandible in the location where the first premolar would normally be located. The lesion appeared cystic but contained a firm shelf on its dorsobuccal aspect that was suspected to be bone. The mandibular left first premolar was absent, and the mandibular left second premolar was more mobile than normal. Lateral and occlusal intraoral radiographs of the cystic lesion and surrounding tissues were obtained (Figure 1).