Equine sarcoids are the most common type of skin tumor in horses. They can occur at any time during the horse’s life, but are most common in young horses. Sarcoid tumors tend to occur at sites of previous trauma, and are most commonly found on the legs, eyelids, and ears. All equines are at risk, including horses, donkeys, mules, and zebras.
There are several different types of equine sarcoids, with the most common being the occult, verrucous, nodular, and fibroblastic. Occult sarcoids are flat and hairless, and, since they do not grow, they are best left alone. If an occult sarcoid is traumatized it may transform in a fibroblastic sarcoid, which can grow rapidly.
Any equine owner who has dealt with the problem of sarcoids knows it is a frustrating issue without a clear and effective cure. There are many options for treatment, most of which are not very successful. Some veterinarians recommend surgical removal if the sarcoid is very large or in a location that interferes with the horse’s ability to function, but there is a high rate of recurrence after surgery. Cryotherapy or laser-assisted excision are options, but also carry the risk of cosmetic damage and recurrence. Other therapies include immune system- enhancing injections and various topical treatments, all of which work to some degree but do not prevent recurrence. Chemotherapy drugs, such as cisplatin and 5-flourouracil, have been used with moderate success but they, too, can not prevent recurrence. Because of the lack of a definite treatment, equine owners have tried formulating their own cures, some of which are surprisingly successful. Topical application of a certain brand (and only that brand) of toothpaste has an underground following in certain circles.
Ohio State University Veterinary Teaching Hospital in Columbus, Ohio, has pioneered a protocol using external beam radiation to treat equine sarcoids, with good outcomes. External beam radiation is preferable to a previous therapy that involved implanting sarcoids with radioactive seeds that continuously emitted radiation. With implanted radiation, horses are radioactive during treatment, which poses a hazard to their human caretakers for the duration of the treatment. With external beam radiation, the horses are not radioactive and can be handled normally. OSU has had good success with this treatment, which involves surgical trimming of the sarcoid followed by four weekly treatments of radiation. Rates of recurrence are much lower with external beam radiation than with other treatments.
For more information, or to view pictures of sarcoids before and after treatment, visit www.vet.osu.edu.