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With everyone staying home right now, people are taking a closer look at their horses, which can lead to owners noticing a lump or bump that was not ever noticed before. So let’s talk about the different abnormalities you might see, and what to do about them.


A common skin tumor in horses, sarcoids are caused by a bovine papilloma-like virus and are spread from cows to horses through infected fly bites. These tumors can range anywhere from a few millimeters in size to huge tumors taking up large areas of the body. Typically, they are hard and scaly on the outside and can appear anywhere on the body. They can look flat, or they can be a raised nodule. In general, these tumors do not cause an issue unless they are interfering with something like the saddle or bridle. Treating these tumors can be difficult, as any type of removal tends to make the sarcoid angry, and it can come back. And when it comes back, it’s usually worse. Most often, the best course of action is to leave it alone. However, if the sarcoid needs to be removed, we have two options. The first option is to use a product called Xxterra. This is a cream made from Indian Bloodroot that is applied daily for seven days. Over the next month, the sarcoid will hopefully scab over and fall off. If this doesn’t work or isn’t feasible, the other option is to inject it with extract of Indian Bloodroot. This will cause a local tissue reaction, and stimulates the immune system to recognize the tumor as foreign and try to kill it.


In humans, the term Melanoma is a terrifying cancer. Luckily in horses, it’s not nearly so terrifying, as it’s not usually fatal unless it starts interfering with bodily functions (like urinating or defecating). This tumor is very common in grey horses and occurs because of a mutation in the cells that produce the black skin color. The most common area for them to appear is under the tail and around the anus, or anywhere that doesn’t grow a lot of hair. However, they can also appear on lymph nodes, salivary glands, and internal organs. These are usually small, smooth bumps that can range anywhere from a few millimeters to large tumors. It’s important if you start noticing these tumors to have your veterinarian palpate your horse rectally periodically to check for tumors in the rectum. Tumors that are found here may eventually grow big enough to occlude the rectum and cut off fecal output, which will obviously lead to colic. Melanomas can either be left alone or surgically removed if they are causing a problem. The same tumor doesn’t usually return, however other tumors may appear that are unrelated to the first tumor.

Squamous Cell Carcinomas

This is a skin tumor we see a lot in light-skinned horses, and it’s caused by damage to the skin cells from ultraviolet radiation. These tumors appear first as small, ulcerated sores with irregular margins that continually grow at a medium rate. They usually show up on the pink skin of the eyes, mouth, and genitalia. Eventually, they start protruding from the original sore and become an ulcerated nodule. This is a tumor that should be treated sooner rather than later, as it’s easier to treat a small lesion than it is to treat a large one. Treatment involves removing as much of the tumor as possible and applying cancer drugs. There is currently experimentation with vaccines that have been successful going on. These tumors are not usually fatal in and of themselves, but horses may be euthanized when the tumor grows so big as to be unmanageable, or starts interfering with bodily processes.


A hematoma is a blood filled pocket under the skin, and is usually caused by trauma to a blood vessel that leaks into the space in between cells, creating a pocket. These are usually not hot or painful after the initial trauma pain has worn off, though they can cause stiffness if near a moving structure. A hematoma will usually not have a lot of swelling or heat in the skin around it, and will most likely feel like a water balloon under the skin. Treatment involves lancing the abscess and draining the fluid, then allowing it to heal from the inside out. If a hematoma is left untreated, the blood can become pus as the body tries to reabsorb it, otherwise known as a sterile abscess.


An abscess forms whenever bacteria gets trapped under the skin or in the muscle. The bacteria cause the immune system to produce pus, which fills the pocket around where the bacteria are. Abscesses are usually hot and painful, and horses may seem lethargic or have a fever caused by the abscess. There is also usually a large amount of tissue swelling and heat around the abscess, which is how to tell if it’s an abscess or a hematoma. Treatment involves lancing and draining the abscess, antibiotics, pain medications, and allowing it to heal from the inside out. Abscesses will usually rupture and drain on their own, but may take days to weeks to do so; many owners opt to have the veterinarian lance the abscess as they are usually uncomfortable.


Edema is caused by trauma to an area and is very common in horses. It is common also for the edema to move to the lowest point it can get to as fluid shifts with gravity. Imagine when you sit on a plane too long and your ankles start to swell. The same thing happens with horses. Edema itself is usually not painful, though initial trauma can be. Edema will be different from a hematoma or an abscess because it will not feel like fluid because it does not have free fluid in it. Usually it either feels like jelly under the skin, or can be what is called “pitting edema,” which is where you can leave a fingerprint in the edema. Treatment often involves anti-inflammatories and cold-hosing, and possibly medications to help get rid of the extra fluid.


Most tumors and swellings are not life threatening in horses; however they should still probably be seen by your veterinarian to determine the best course of action for your horse. If you have any questions, as always, contact your veterinarian.