Dermoid Cyst in the Intermandibular Space of a 3-Year-Old Thoroughbred Gelding: A Case Report

• Soft tissue masses, of various etiologies, are a common complaint in equine practice.
• No reports in English written literature of dermoid cysts located in the intermandibular space of a horse.
• First report in literature of a dermoid cyst arising in the intermandibular space of a Thoroughbred.
• Dermoid cysts should be included within the differential diagnoses list of masses in the intermandibular space of horses.

Soft tissue swelling located in the intermandibular space is very common in horses and presents a significant diagnostic challenge. Although the possible etiologies of intermandibular swelling are many, dermoid cysts are rarely included within the differential diagnoses list. This may be due to their low prevalence and to the lack of English written literature reporting dermoid cysts in this location in horses. This is the first report describing the clinical signs, diagnosis, and management of a dermoid cyst arising in the intermandibular space of a Thoroughbred horse. In this case, an enlarging soft tissue mass located in the intermandibular space was diagnosed as a dermoid cyst following complete subcutaneous surgical excision and histopathology.