A congenital malformation of the maxilla of a horse

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