Sarcoids are thought to be caused by the bovine papilloma virus infection, characterized by proliferation of neoplastic fibroblasts and thickening and/or ulceration of the skin. It is the most frequently diagnosed tumor in horses. Surveys have estimated the prevalence of sarcoid at 20% of all equine neoplasms and 36% of all skin tumors.
Sarcoids occur at any age but are more common in young adult horses. These tumors may be single or multiple and, although they occur most frequently on the head, limbs and abdomen, they can occur anywhere on the body including sites of trauma and healed wounds. Even though all breeds are affected, a generic predisposition to sarcoid development may exist. Quarter horses, Appaloosas and Arabians may be at greater risk and Standardbreds at lower risk to develop sarcoids. There is no gender, coat color, seasonal or geographic predilection for the occurrence of the sarcoids.
The appearance of sarcoids varies from small, sessile or pedunculated growths that have a warty appearance to firm, freely moveable, nodular dermal masses. Sarcoid diagnosis is based on the characteristic microscopic arrangement of fibroblasts and collagen fibers and their orientation to the overlying epidermis. There are many approved methods for treating sarcoids, some of which include surgical excision, cryotherapy, immunotherapy, radiotherapy, laser therapy, hyperthermia, topical chemotheraphy and intratumoral chemotherapy. Treatments may have to be repeated. Sarcoids are locally invasive and frequently recur after surgical excision, but do not metastasize.
Treatment is tailored to the patient but generally involves surgical removal of the lesion followed by ancillary treatment of the remaining surrounding skin. Ancillary treatments include
- The use of anti-neoplastic agents (e.g. cisplatinum) applied topically or injected directly into the tissue
- Freezing the tissue with liquid nitrogen (cryotherapy)
- Injection of the tissue with an immune stimulant
- Radiation therapy.
A series of biweekly to monthly treatments is often required to be successful. It is very important to attack the tumor aggressively at the onset, as failure to do so often results in growth of a more resistant sarcoid tumor.
Tumor treatment should be pursued only if the horse has a current tetanus vaccination or is given one simultaneously. Antibiotics may also be administered to prevent against bacterial infection during tumor necrosis (death) and wound healing.
The chance for a successful outcome is always increased if treatment is started when the size of the tumor is small. Don't wait and see if the tumor disappears on its own.
Wounds that are sutured should be kept clean and dry for 2 to 3 weeks. Sutures or skin staples will be removed at 10 to 14 days. Wounds that are not sutured should have the skin surrounding them cleaned once to several times a day to prevent irritation from the fluid discharge from the wound. Cleaning the surface of the open wound is dependent on the original method of treatment. In some cases very gentle cleansing with warm water is required, while in other cases this is contraindicated.
Continuation of oral or injectable antibiotics may be necessary for a short period of time.
There is currently no method or vaccine available to prevent the occurrence of a sarcoid. The best advice is to make sure that your horse lives in a safe environment to minimize his chance of getting a skin injury that may then become an entry site for the virus.
Horses that have had a previous sarcoids are at risk to develop a sarcoid in the future. Always bring to the attention of your veterinarian the presen