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Lumps, Bumps and Sarcoids


By Jennifer Dunlap, DVM
While skin cancer and benign growths are uncommon in horses, when they do occur they need to be treated early to achieve the best possible outcome. It is important to run your hands over your horse frequently to check for any lumps or growths and keep an eye on high risk areas such as pink skin around eyes.

If you own a gray, my favorite horse color, you are likely aware that most gray horses will develop melanomas as they get older. They are most commonly found around the anus, under the tail, around the teats in mares, sheaths in male horses, and around the corners of the lips. They will typically look like small bumps under the skin. Luckily for most horses, the melanomas remain benign and never cause a problem.  Occasionally melanomas can form in and around the salivary glands and lymph nodes of the throat and, in extremely rare cases, they can form internally or within the bone marrow. 

Melanomas in the common locations can be a problem if they start to grow and/or ulcerate. These horses require treatment. If it is a single melanoma, surgical removal, laser or cryosurgery can be successful. But the majority of the time, the melanomas are in clusters and, in these cases, oral medications such as cimetidine can be used to help control growth and spread of the melanomas. 

Melanomas around the lymph nodes and salivary glands around the throat can be dangerous. They cannot be surgically removed due to the structures, nerves, ducts, and vessels surrounding them, so oral medications can be used to help control their growth. But in some cases they can start to press on the airway or the back of the throat and make swallowing difficult. It is important to check the throatlatch area of gray horses as they age and, if a growth is felt, get it checked out and put the horse on medication if it is a melanoma. This is not an area that should just be watched.  Horses with melanomas in this area should be on medication. 

If your horse has a lot of pink skin around his/her eyes, it is very important to watch the eyelids, including the third eyelid, for precancerous lesions, which can often appear as scalloped slightly thickened tissue, cauliflower-like growths, or a non-healing scab.  Horses with pink skin around the eyes are prone to squamous cell carcinoma, which can be very locally invasive and in rare cases metastasize.  It is a good idea to use a fly mask on these horses when they are turned out to protect them from the sun.  This can go a long way towards preventing squamous cell carcinoma.  If any changes in the lids occur, have them checked out by your veterinarian, who will likely do a biopsy or refer you to an ophthalmologist and then you can discuss options for treatment. Surgical removal can be successful if the lesion is small. It is critical to maintain lid function so that the eye can be continually bathed in tear film. So if a lesion is so large that the lid or a portion of the lid will have to be removed, the eye may have to be removed as well.  This is why it is so important to catch these lesions early so that the eye can be preserved. Having said that, it is not the end of the road if a horse has to have an eye removed. Horses can do very well with only one eye, given their wide range of vision.

Squamous cell carcinoma can also crop up on the penis and sheath area and it is not limited to only pink skinned horses in this location.  The best way to prevent squamous cell carcinoma in this area is to perform routine sheath cleanings one to two times per year.  Smegma is the "goo" that forms within the sheath from dead skin cells, sweat, skin oils and dirt.  A large build up of smegma is associated with an increased risk of cancer.  Some male horses, including stallions and some geldings, never build up much smegma, but many geldings build up large lumps of smegma that irritate the skin of the penis and sheath.  Some horses are violently resistant to cleaning of this area, so sedation and veterinary attention may be necessary, especially if you notice abnormal growths, reddened areas, or thickened areas.  It is important to clean this area correctly, so have your veterinarian show you how to do it to avoid injuring your horse or yourself. This is a delicate area so cleaning with harsh detergents or mineral oil is not recommended.  The best thing to use for sheath cleaning is Excalibur, a product made specifically for this task.  It is available at TSC and other tack shops. Cleaning too often can unbalance the good bacterial flora in this area and cause irritation, so once or twice year is usually plenty.  Often this can be done when your gelding is sedated for other procedures.  If there are abnormal growths or skin irritation your veterinarian will likely perform a biopsy and then discuss options for treatment including surgery.

Sarcoids are by far the most common skin tumor. They don't fit neatly into any category and there is still some discussion about what they are and what causes them.  But they seem to be closely associated with the bovine papilloma virus, which causes skin growths in cattle. They are locally invasive and their danger depends on their location on the body, and if they are growing or ulcerating. For example, a sarcoid that is quiet, never grows, and is located on the rump may never need to be treated. But a sarcoid that is on a lower leg and is growing will have to be treated due to the likelihood that it will damage the structures of the lower limb.

There are different types of sarcoids based on the appearance of the sarcoid, ranging from verrucous (wart like) to fibroplastic (fleshy, ulcerating.) There are several important things to remember about sarcoids including that they are transmissible from horse to horse or from one site on a horse to another.  If you use a brush on one horse's ulcerated sarcoid and then brush another horse with a wound, the sarcoid can invade the second horse's wound. Sarcoids also send hair like projections deep into the skin so they are locally invasive.  Your veterinarian should be able to help you decide whether or not a sarcoid needs to be treated or removed.  Sarcoids around the eye, the lower limbs, areas where the tack continues to rub, that are growing or ulcerated will need to be treated.  Treatment options depend on the size and location of the sarcoid. In some areas surgical removal is possible.  Deep margins must be obtained to get all of the sarcoid and the growth should be sent off to a pathologist to check those margins for complete removal.  Treatment with an ointment called Xterra or topical chemotherapy such as 5-fluoro-uracil can be very successful for some growths.  Some sarcoids can be removed with cryosurgery.  Some sarcoids are aggressive and will require a variety of treatments to fully remove them. 

[Editor’s note: Don Silver at Herbs4Horses explained, “Xxterra is Bloodroot made into a paste. This stuff is also known as Indian Blood. It is very toxic to the touch. You must use gloves and not get it on you. It burns the sarcoid.  It will work, but it does nothing to prevent them from coming back. You have to cure from inside to prevent it from reforming.”]
Early intervention is the key to keeping skin growths from causing major problems for your horse.  Discussing any strange lumps, bumps, or growths with your veterinarian is essential. With early intervention, your horse will require less invasive treatment and get on the road to recovery much sooner.

Additional Resources:

“Skin Problems: A Better Sarcoid Treatment.” Health article at American Association of Equine Practitioners (AAEP) website, March 19, 2009.
You may find additional articles of interest on the AAEP website; browse “skin problems” under Health Articles.
Goetz TE, Ogilvie GK, Keegan KG, Johnson PJ. “Cimetidine for treatment of melanomas in three horses.” Journal  American  Veterinary  Medical Association. 1990 Feb 1;196(3):449-52.
Katherine Burden. “Melanomas and their effect on the grey horse.” Young Scientists Journal, The King's School, Canterbury, United Kingdom. 2011, vol. 4, issue 10. Posted online Jan. 2012.;year=2011;volume=4;issue=10;spage=75;epage=81;aulast=Burden
For more information about Xxterra, visit:

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