A large type Va dermoid sinus (true dermoid cyst) on the dorsal thoracic region in an English Springer Spaniel dog

Abstract A 3.5‐year‐old, male, neutered English Springer Spaniel dog presented for a large subcutaneous mass on the dorsal thoracic region. Magnetic resonance imaging and computed tomography scan confirmed a fluid‐filled subcutaneous lesion with no evidence of connection to the spinal cord. Complete surgical excision was performed. Histopathological examination was consistent with a dermoid sinus. A seroma developed post‐operatively and was successfully managed surgically. The patient made a full recovery. This is the first reported case of a type Va dermoid sinus on the dorsal thoracic region in an English Springer Spaniel dog.