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Lumps and Bumps

What are they, and what can be done?

Our horses’ coats change from sleek to furry as the winter winds gather, but whatever the season, the skin underneath usually feels smooth and pliable. So what should you think if you discover a lump in your horse’s coat? Lumps and bumps, ranging from the diameter of a pea to that of a walnut, are relatively common in horses. Three common types of lumps are sarcoids, collagen granulomas, and melanomas.

Sarcoids are growths that cause areas of skin to lose hair and assume a wart-like, dry, gray appearance. They are benign in that they do not spread internally, but can wreak havoc if they occur near the eye or if they enlarge substantially. Sarcoids are often found in the ear, but they can occur any-where on the body. Most are coin-sized but they can enlarge over time. Some turn into lumps that are raised and firm; others stay relatively flat. Raised sarcoids respond better to treatment than those that are flat. Treatment choices include cryotherapy (freezing the lumps), laser surgery, and injection of the lesion with chemotherapy or immunostimulants. The newest therapy available is a topical herbal paste called Xxterra®. It is thought to alter the sarcoid cells, and by doing so stimulates the immune system to mount a response to reject the sarcoid.As with all types of lumps, treatment is most successful when the sarcoid is small.

Collagen granulomas are raised, hard bumps usually found in the area where the saddle tree or girth sits. They rarely exceed one inch in diameter. Hair over these lumps is sometimes thin, and the horse may be bothered by pressure on them. Collagen granulomas are essentially an odd type of scar tissue that forms on some horses as a response to pressure from tack or hypersensitivity to insect bites. Most can be shrunk by a local injection of cortisone, but some horses have recurrent granulomas that need frequent injections or special pressure-relieving saddle pads.

Melanomas are lumps that are found most often in gray horses. About 80% of all grays that are over the age of 10 have melanomas somewhere on their body, usually on the tail or around the anus. Sometimes melanomas are also found in the mouth, near the throat latch, or on the udder of mares or the sheath of geldings. They vary from blueberry- to walnut-size and appear black or dark blue through the skin. If you find one melanoma, you will usually find more if you look, and they often enlarge or multiply over time. Although melanomas are a cancerous growth, they rarely spread internally. Surgery is sometimes performed to remove individual melanomas that are bothersome. Often the best course of action is to leave the growths alone as it may be impractical to operate on all the sites, and recurrence is expected.

Sarcoids, collagen granulomas, and melanomas are common kinds of equine skin bumps, but there are dozens of other more unusual growths with a similar appearance. If you find one or more lumps on your horse it’s best to have one of the vets examine it. We may decide to biopsy the bump to find out exactly what it is. Most lumps are not very dangerous, but some are cancerous and others may interfere with the work the horse performs. A veterinary examination is the best way to find out if a lump needs treatment or just monitoring.