My yearling Standardbred colt has been diagnosed with a dentigerous cyst by the veterinarian. Can you possibly give me some information on this type of cyst?

Dentigerous cysts, also known as temporal odontoma, temporal teratoma, heterotrophic polydontia, or ear teeth, are relatively rare but well-documented occurrences in young horses. They are composed of sacs containing a tooth or dental tissue that develop where there should not be a tooth.

Most commonly, they occur near the base of the ear and present as a firm swelling sometimes with a draining tract discharging a thick, white fluid. They can, however, appear inside the skull or nasal cavities, where they are much more likely to cause trouble, either by pressure or obstruction.

Since they are true cysts, they are lined by a secretory epithelium (a lining that produces some substance), and they must be surgically removed in order to eliminate the drainage. They are a developmental anomaly and are not considered cancerous tumors, so malignancy is not a risk. Good-quality radiographs are usually diagnostic and complete surgical removal is curative