What is Skin Tumors (Equine Sarcoid)?
The appearance of sarcoids can vary significantly, and can be flat, wart-like, elongated, fibrous, or even resemble proud flesh. While they do not spread into distant areas, they can spread locally and grow, often after trauma or injury to the tumor. They often form from scar tissue or sites of a previous wound or trauma, and can prevent a wound from healing. Most often seen in the genital region, these tumors can form anywhere on the body. In some cases, they can extend into the lymph nodes. The malignant form of sarcoids is the most dangerous, as there is no available treatment for this aggressive tumor.
Equine sarcoids are growths that can take on various forms. Rarely life threatening, these tumors can become aggressive, and can invade and irritate local tissues, compromising function. Believed to be caused by the Bovine papillomavirus, these sarcoids are a very common skin tumor in horses. Many treatments are available, although recovery can vary based on the aggressiveness of the tumor.
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Symptoms of Skin Tumors (Equine Sarcoid) in Horses
The main symptom of equine sarcoids is the presence of the tumors themselves. They can vary in appearance, and can mimic growths or tumors associated with other conditions. Some types of sarcoids seen are:
- Small wart-like lesions
- Ulcerated, nodular areas
- Large, fibrous growths
- Flat, plaque surfaces
- Small bumps under the skin
- Scaly lesions
- Proud flesh, or excessive granulation tissue growth
- Benign fibropapillomas
- Pedunculated tumors, or a mass on an elongated stalk of tissue
- Tumors with serum discharge
Sarcoids can develop anywhere on a horse’s body, but are most common in these areas:
- Genital areas
- Around the eyes and on eyelids
- Sites of past injury, wounds or scarring
- Sites where other kinds of sarcoids were injured
- Surgical wounds
There are many different kinds of sarcoids, each with varied features, growth patterns, and behaviors. The six most recognized are:
These are flat, hairless circular areas that grow slowly or not at all, and are common in areas of the body with less hair. They can contain one or more nodules, and can alter texture and color of hair coat. If they are injured or biopsied, they can evolve into verrucous or fibroblastic sarcoids. While they can remain stable and harmless for many years, progression into more dangerous types of sarcoids can occur even without trauma.
These are scabby, gray or wart like lesions that can be flaky, scaly, or ulcerated, with both flat and pedunculated characteristics. Small nodules can also be seen, as can the appearance of blistering. They can be limited to local areas, or extend to wider areas of the body. They are slow growing and not aggressive until injured, when they can change into fibroblastic sarcoids.
These are firm, spherical nodules of variable size that can ulcerate or bleed. They can occur singularly or hundreds at a time. Sometimes they seem movable under the skin, while at other times, they can have deep attachments deep within the skin. The skin over the tumors can be thin and ulcerated, causing them to be more aggressive. Any trauma also causes increased aggressive behavior.
These are fleshy masses that can bleed easily, and may have a cauliflower like appearance due to the hemorrhagic surface. They can also take on the appearance of proud flesh, or exuberant granulation tissue, and can grow slowly or quickly.
These are sarcoids that combine the characteristics of two or more types. It can also represent transitional stages between two different types. They can become increasingly aggressive as they become more fibroblastic, or due to biopsy or trauma.
This is a rare and aggressive tumor that can become widespread through the skin, and can intersperse with nodules and fibroblastic masses. The spread over a horse’s body can be extensive. They can be particularly dangerous when formed near the eye.
Causes of Skin Tumors (Equine Sarcoid) in Horses
The causes of equine sarcoids are believed to be viral and genetic factors.
- Types 1 and 2 of the Bovine papillomavirus (BPV)
- Genetic predisposition, such as with the Quarter Horse breed
While researchers are not entirely sure how the Bovine papillomavirus is transmitted to horses, theories include:
- Transmission by fomites or biting flies
- Transmission through contaminated tack or pasture
- Presence of BPV in old wounds that can be stimulated into action with trauma
Diagnosis of Skin Tumors (Equine Sarcoid) in Horses
A diagnosis of equine sarcoid can be difficult, as lesions can resemble those of other conditions. The presence of multiple tumors, often of varying types, can lead to a diagnosis. A positive identification of the presence of BPV can be made based on the results of a biopsy. However, the process of obtaining the biopsy can aggravate the tumors, causing them to be more aggressive and expand. A needle aspirate can be used to collect cells for examination, although false negative results are common.
Due to the risk of aggravating the tumors, your veterinarian may make a presumptive diagnosis of equine sarcoids on the basis of appearance of the tumors, or if there is a wound that fails to heal.
Treatment of Skin Tumors (Equine Sarcoid) in Horses
If the sarcoid is small and in a location that will not cause trouble, a benign neglect approach may be recommended, wherein you should monitor the tumor at least once a month for any changes. Treatment may not be needed for those sarcoids that stay the same. Some tumors can recede without treatment.
Treatment aims to remove the tumors, taking care to excise every abnormal cell, or the tumor may return. Removal can be accomplished in many ways. Litigation using rubber bands to suture tumors can be used in combination with a topical preparation in cases of pedunculated sarcoids. Cryotherapy uses liquid nitrogen to freeze and kill tumor cells. Surgical and laser excision can be used to remove sarcoids. Radiation therapy can be effective, but dangerous in some areas, such as near the eyes. Chemotherapy injects the tumors with drugs to kill tumor cells. Other treatments include local immune modulation therapies and various topical creams that can treat wounded tissues after surgeries, kill the tumor cells, modulate the immune system, and induce tissue necrosis.
Larger and more aggressive tumors may need a combination of multiple treatments, and many therapies can aggravate the tumors. In many cases, tumors will return. Malignant tumors are particularly hard to treat.
Recovery of Skin Tumors (Equine Sarcoid) in Horses
The rate of recovery is dependent on the type of sarcoid present on your horse, on the type of treatments used, and on the reaction of the sarcoid tumors to treatments. Prognosis is very guarded, as tumors have a high incidence of reoccurrence, and serious complications can occur from the disease and therapies employed. Sarcoids that have been excised can regrow in a more aggressive fashion within 6 months. Multiple treatments may be required.
You may need to monitor tumors on your horse for an extended period of time. For some tumors, you may be able to use topical creams to burn away the tumor cells. More often, multiple veterinary visits will be needed, as well as any supportive therapies and wound management.
Skin Tumors (Equine Sarcoid) Questions and Advice from Veterinary Professionals
My 32 year old horse started developing a verrucose sarcoid on his face/jawline about 5 yrs ago. The vet determined to just watch it. It is very slow growing and is about the size of a small grape. It is hidden fairly well under his hair except when it starts to bleed. It looks very warty & bumpy. I believe it has changed into a fibroblastic tumor due to him hitting and rubbing it causing bleeding and cracking of the tumor area. I usually clean it with tincture of iodine and spray it with blue kote or another anti fungal/ bacterial spray and it drys up and settles down in a few weeks. Lately he's seemed to be a little more grouchy. Today I called him into his stall and he had a tear of a piece of skin with thick winter hair still attached, that was kinda puffing and hanging out around the sarcoid tumor. As I felt of it, i could tell that the skin & hair was no longer attached to the flesh on his jaw area, where the sarcoid is. As I began to continue to remove the skin/hair layer it peeled off in a circular area of exposed red flesh about 4 inch diameter. No bleeding at all. I pulled off a little more hair that was crusty and scaly around the same area. The flesh is all dry under the skin pocket, except for the sarcoid tumor. It was smaller in size but red, bumpy and oozing. It was just an empty pocket of dried skin that had been surrounding the sarcoid tumor. Part of the tumor head was dried up and still embedded in the "skin pocket" that i peeled away. I cleaned the exposed flesh and sarcoid tumor with tincture of iodine mixture and sprayed with some blue kote anti fungal/bacteria spray. I am concerned about putting him outside in our below freezing weather, and what it may do to his exposed bare flesh on his jaw now. Any suggestions as far as wrapping it, to keep it from the elements or not to worry about it being able to freeze, since it has no hair? What would you suggest? Thank you
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