PARAESOPHAGEAL CYST IN A HORSE

A 2 year old Morgan gelding was evaluated for a non-painful mass located caudodorsal to the larynx. Radiographically, the mass was ovoid shaped and had a peripheral rim of mineralization. Slight ventral displacement of the dorsal margin of the trachea could also be identified. Uniform moderate level echoes were seen throughout the interior of the mass on ultrasound examination. An esophagram was performed and demonstrated displacement without involvement of the esophagus by the mass. The esophagus appeared as a separate structure from the mass on both the ultrasound examination and esophagram. During surgical removal, the mass also appeared as a distinct structure from the esophagus. Histologically, the mass was consistent with an epithelial inclusion cyst which originated from the esophagus.     

OSSIFYING AMELOBLASTOMA IN A HORSE

The features of an ossifying ameloblastoma in a 5-year-old gelding are described. The tumour developed in the angle of the right mandible and microscopically consisted of multiple follicles and islands of epithelial tissue adjacent to which were trabeculae of bone, osteoid and compact collagenous tissue.     

PRESUMPTIVE TENOSYNOVIAL OSTEOCHONDROMATOSIS IN A HORSE

A 5 year old Arabian mare was evaluated for a non-painful swelling located dorsal to the right carpus which had been present for 2 years. Radiographically, multiple mineralized bodies were identified dorsal to the distal radius and carpus in the region of the tendon sheath of the extensor carpi radialis muscle. The radiographic appearance of the carpal bones was within normal limits. On ultrasound examination, multiple hyperechoic foci with posterior shadowing were seen adjacent to the extensor carpi radialis tendon. There was minimal distension of the tendon sheath and no abnormalities within the substance of the extensor carpi tendon were identified. Considering the radiographic and sonographic findings, a presumptive diagnosis of tenosynovial osteochondromatosis was made. Histological confirmation of this diagnosis was not obtained as the owner declined further diagnostic evaluation.     

A CONGENITAL MALFORMATION OF THE MAXILLA OF A HORSE

A 1-month-old male American Paint Horse was evaluated for a hard swelling on the right side of the maxillary region. On radiographs there was a large, expansile outpouching of the right maxillary bone between the second and third premolar teeth. Computed tomography further characterized the expansile lesion to have a soft tissue component and to originate in the region of a caudal maxillary tooth. Surgical reconstruction of the defect was unsuccessful and the animal was euthanetized. Based on failure to find histopathologic evidence of a neoplasm or cyst, the diagnosis was a congenital malformation.