Nasopharyngeal epidermal cyst in a dog.

Plain film radiography, magnetic resonance imaging, and histologic evaluation were used to diagnose nasopharyngeal epidermal cyst in a 12-year-old male Miniature Poodle with inspiratory stridor. The cyst was lined with stratified squamous epithelium, with variable keratinization. Most of the epithelium was well-differentiated and supported by a fibrovascular tissue separating it from underlying woven bone. One margin of the mass had a transition from stratified squamous to columnar respiratory epithelium. Other reported epidermal cysts in dogs have been confined to the middle ear or intracranial area. This case was unique, because the mass was located in the nasopharyngeal area, causing airway obstruction. This lesion was most likely acquired rather than congenital, because the dog had a history of middle ear inflammation, as well as bite wound trauma to the throat region. The mass was successfully removed by use of a transpalatal approach, and signs attributable to respiratory obstruction were alleviated. The dog had no abnormal clinical signs several months after the procedure.