What Is A Sarcoid On A Horse? The Unique Equine Tumor

Tumors and cancer are both conditions commonly found in humans and are just as common in horses. Different types of cancers appear for a variety of different reasons. In general, you may find skin cancer along with various types of internal cancers, but many show up wherever they want when they want. Many cancers are not particular when it comes to their host, but what is a sarcoid on a horse?

What Is a Sarcoid On a Horse? Cancer, Tumour, or Both?

A common skin tumor found only in horses and ponies, that at first glance it may look like warts, but it is more likely a Sarcoid Tumour. Sarcoids are very destructive at the location site, so many vets consider a Sarcoid a form of skin Cancer.  Although it is not yet clear as to how Sarcoids initially developed, research is showing indication of being linked to bovine papillomavirus. 

What Is a Sarcoid On a Horse? Cancer, Tumour, or Both

Sarcoid Locations

Sarcoids are most common in young to middle-aged horses and most often have a genetic predisposition for possible sarcoid growth. You will usually find these growths on the horse’s abdomen, inside the hind legs, around the sheath, chest, and around the eyes and ears. Scars from previous wounds are also common sites for Sarcoids to grow. 

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What Do Sarcoids Look Like?

Tiny lumps that appear in clusters or as single tiny lumps. As the Sarcoid gets bigger the skin often ulcerates and will become infected. In summer the cancer site is very prone to attracting flies, resulting in open sores that do not heal easily. If a Sarcoid is small a horse’s coat can easily conceal the growth. Sarcoids come in a variety of shapes, sizes, and textures.

Some are smooth while others are rough. They can have skin lumps or nodules and a similar look to cauliflower. Some Sarcoids will become very aggressive and be considered fibroblastic or malevolent, while others maintain their same shape and size, and in some cases will clear up without any type of treatment.

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Sarcoid Treatment In Horses

Treating Sarcoids is very important and should be taken seriously. Often if a Sarcoid grows others will grow elsewhere on the horse’s body. Treatment is most effective if started early on before the Sarcoid becomes large, making it more difficult to remove. Several treatment options are available but there is no magical cure and there is a high risk of the Sarcoid returning.

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Treatment Options

Surgery – Surgical removal of a Sarcoid has a very high failure rate. The wound in most cases heals poorly, and the Sarcoid will usually come back. 

Ligation – This can be a very painful option for the horse, especially if the Sarcoid is located in a delicate area. A tight band is placed around the base of the tumor and will cause it to fall off. There is a very high risk of tumor cells being left behind and causing the Sarcoid to regrow. 

Cryotherapy – Under general anesthesia for pain, the tumor can be destroyed by freezing it. This treatment requires multiple lengthy treatments for treatment to be done safely and effectively.

Immune Therapy – Under heavy sedation, treatments involve an injection of BCG to stimulate the horse’s immune system to eliminate the tumor. There is a risk of reaction with this treatment so premedication is advised. 

Topical Treatment – Special creams, of high metal makeup, have been successful in some cases, usually with smaller lesions. 

Radiation Therapy –  This can be very effective as a treatment but the danger of radiation exposure makes this a very expensive choice and also requires the horse to be under general anesthesia. Radiation therapy can only be done at specialized centers due to the technical difficulties involved. 

Laser Removal – This treatment is a relatively new treatment option, but under standing sedation, with local anesthetic or under general anesthesia a surgical laser is used to remove the tumor. 

With all treatment options treatment must continue until there is a positive response to the treatment. If treatment is stopped before the Sarcoid is eliminated, there is a strong possibility of it returning and in most cases will appear worse than the original lesion. 


Sarcoid tumors are not life-threatening. Their development can be annoying for the horse if it is located in a place that is irritated by tack or other areas that can produce friction. Horses can live a relatively normal life even if Sarcoids are present throughout their lifespan.

Providing treatment and trying to maintain a Sarcoid small in size will help with the chances of infection and/or irritation. Follow the treatment plan you receive from your vet for the elimination of the remaining Sarcoid cells. 

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