Dermoid sinus, dog

Multiple dermoid cysts are evident along midline of this dog's face and head. The dog was adopted as a young adult with an unknown history, with a lesion that was presumed to be a scar. When recurrent drainage occurred, the patient was treated with multiple rounds of antibiotics, and the lesion was investigated for foreign body or bony sequestration. After progression to the stage seen below, hair was visible within the exudative cysts after clipping; the diagnosis was confirmed on histological examination. Surgical excision was performed.