Solid Tumors in Horses: Characteristics and Treatments

Skin and subcutaneous (under the skin) tumors in horses comprise 50-80% of all equine neoplasia (tumors).

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While tumors are a relatively common occurrence in humans, horses aren’t as likely to develop these growths on their bodies. However of those that develop, skin and subcutaneous (under the skin) tumors in horses comprise 50-80% of all equine neoplasia (tumors). At the 2011 American College of Veterinary Internal Medicine Forum, held June 15-18 in Denver, Colo., Jeff Phillips, DVM, Dipl. ACVIM, assistant professor of oncology and genetics at the University of Tennessee College of Veterinary Medicine, discussed characteristics and treatment of equine sarcoids, squamous cell carcinomas (SCC), and melanomas in horses.


Phillips began discussing sarcoids and their different forms: nodular, fibroblastic (cauliflowerlike appearance), verrucose (flat), and sarcoma (loss of epithelium overlying the tumor). He noted that equine sarcoids are strongly associated with bovine papilloma virus, and the amount of viral DNA found in each tumor correlates with disease severity. While its mode of transmission is unknown, this virus can be detected in flies and in the environment, and researchers believe it could be transmitted via fomites (grooming tools, tack, etc.) rather than direct horse-to-horse contact. The most common sites of sarcoid formation are areas that have experienced some trauma in the past, such as the girth area.

"Sarcoids are not thought to be heritable," noted Phillips

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Written by:

Nancy S. Loving, DVM, owns Loving Equine Clinic in Boulder, Colorado, and has a special interest in managing the care of sport horses. Her book, All Horse Systems Go, is a comprehensive veterinary care and conditioning resource in full color that covers all facets of horse care. She has also authored the books Go the Distance as a resource for endurance horse owners, Conformation and Performance, and First Aid for Horse and Rider in addition to many veterinary articles for both horse owner and professional audiences.

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