Sarcoids are benign skin tumours and are the most common tumour to affect the skin of horses. They can appear anywhere on the horse’s body but are most common in the armpit area, inner thigh, and around the eyes and ears.

Any horse can be affected and horses that have previously had sarcoids are more likely to develop them in the future.

Whilst some sarcoids can remain stable and unchanging for long periods, they are unpredictable in their growth and development and can suddenly enlarge without warning.

As sarcoids can affect the use of the horse, become infected, or otherwise cause detriment to the horse’s welfare they should always be assessed by a vet and, where appropriate, treated.

Numerous treatments are available for equine sarcoids. These can be divided into two broad categories: Surgical removal of the sarcoid tissue, and topical treatments to cause the sarcoid to die back.

Surgical removal

Conventional surgery, with a scalpel, is applicable in some cases, but can have a high sarcoid recurrence rate, reportedly up to 82%. As with other surgical techniques this may be undertaken with the horse under general anaesthesia, or, may be done under standing sedation with the use of local anaesthetic.

Traditional surgery has, therefore, been largely superseded by surgery using either a laser or a harmonic scalpel.

Laser surgery can be costly but has a far reduced incidence of sarcoid recurrence as the surgical site is at less risk of contamination with tumour cells.

This is due to the fact that the laser does not cut tissue but vaporises and ablates the tissues it comes into contact with.

The downside of laser surgery is potential collateral damage to tissues around the surgery site and in most cases the surgical site cannot be sutured closed afterwards so a prolonged healing time is expected.

A harmonic scalpel is an instrument that can simultaneously cut and cauterise tissues using ultrasonic vibrations.

This can be used with greater precision than a laser, with less collateral damage, and the skin can usually be sutured following surgery, resulting in faster healing and an improved cosmetic affect.

Cryosurgery (freezing): can be used for small sarcoids. By repeatedly freezing and thawing the tissues tumour cells are destroyed.

Unfortunately, this technique will often result in scarring and carries a high risk of sarcoid recurrence. Cryosurgery may be combined with other types of surgery in some cases.

Topical treatments

Many topical treatments are available for the treatment of equine sarcoids. The best known in the UK is AW5 cream (‘Liverpool cream’). This cream has to be ordered by a vet, on a case by case basis, and can only be applied to the sarcoid by your vet, usually over a period of several days. This cream can be painful to the horse and can result in a significant local reaction, necessitating pain relief.

Bleomycin is a chemotherapy cream used in humans to treat certain types of cancer. It has recently been shown to be very effective in treating certain types of tumours in horses, including sarcoids. Given the success seen with this drug so far it is likely to be widely used to treat sarcoids in the future.

Radiation therapy may be applicable for treatment of equine sarcoids in certain cases, with excellent results. This is, however, very expensive and is only available in a few locations. It is usually reserved for particularly difficult to treat sarcoids. In the UK this is currently only available at the Animal Health Trust.

As can be seen there are many different treatment options for sarcoids, and the approach to each case must be judged on its own merits. Whichever treatment is chosen it is important that any suspect sarcoid be assessed by a vet to ensure the best outcome for both owner and horse.