Tumor. Now there’s a word guaranteed to strike fear into anyone’s heart. Loosely defined, a tumor is an uncontrolled or incorrect growth of cells, which can invade normal tissue and disrupt functions. It can be benign (meaning it’s slow-growing and doesn’t tend to spread) or malignant (a fast-growing, aggressive tumor that easily metastasizes, or spreads to other tissues). We’re not immune to tumors, and neither are our horses.

The good news, if you can call it that, is that the vast majority of tumors that affect horses are of the benign variety. Cancer isn’t nearly as common a killer in equines as it is in humans. In fact, the two most common types of tumors in horses—melanomas and sarcoids— usually are benign and often cause little disruption in a horse’s daily life. Some horses have been known to live with these skin growths for upward of 20 years. Under certain circumstances, however, both of these types of tumors can be a nuisance and a health risk, not to mention unsightly. Let’s take a look at each type of tumor, then examine some of the newest research ideas and treatment options.

The Sarcoid Scenario

You’ve probably seen a sarcoid tumor on a horse at some point in your travels; they’re the most common type of skin tumor in equines, occurring in an estimated one out of every 100 horses. The word sarcoid is a contraction of the word sarcoma (a tumor originating from the connective tissue) and the suffix "-oid,” which means "like.” So, a sarcoid is a tumor "like a sarcoma.” The difference is that sarcomas generally are malignant, and sarcoids usually are not