The doctors at Equine Medical Service were requested to evaluate and diagnose a four year old mare for a mass on the front of the cannon bone of the left fore leg. This horse has had a sarcoid around her eye that was treated surgically and topically two years previously. The mass was removed and submitted for microscopic diagnosis of the tissue. Where the mass was removed from the leg was sutured and eventually healed. About fifteen months later the horse was presented to the doctors of Equine Medical Service for evaluation of a recurrence of a mass in the same area as before. The treatment plan was to surgically de-bulk the mass and treat the area locally with a chemotherapeutic drug. About 3 weeks and again at about twelve weeks post operation the wound area was injected locally with a chemotherapeutic drug.
At about 14 months post operation the leg has residual scar tissue, but no evidence of sarcoid tissue or lameness in that leg.
Sarcoids usually appear as large, cauliflower like warts. They are the most common type of tumor in horses. The specific cause of sarcoids is not known, but a virus is thought to be involved. Occasionally a group of horses has a high incidence of sarcoids, but sarcoids are not contagious. Sarcoids may occur at sites of previous trauma, possibly allowing a causative virus to grow at the injured site. Heredity may also play a role. Certain individual horse lines or breeds may have a higher incidence of sarcoids. The tumors may respond to vaccines and other immunostimulants.
Sarcoids can have quite large, flat bases and can occur in areas that are difficult to treat, such as on the ears, around the eyes, and on the coronet. Those occurring over muscular areas are easier to treat. There are many different treatments for sarcoids, but they often recur after treatment. Recurrence depends on how long the sarcoid has existed, and the number and size of the sarcoid(s). After previous removal, they are more resistant to complete removal. Keeping your horse in a clean environment and reducing insect contact is important.