Squamous Cell Carcinoma – Skin Cancer in Horses

Most people who have been around horses long enough have probably heard that White horses are very susceptible to cancer. I recently found myself in the disheartening position of learning that my horse, Rio, had squamous cell carcinoma on his eyelid.

At first, I viewed the small bumps on his eyelid as harmless. However, I took pictures so that I could monitor the growth of these bumps. Luckily, just a short time later, during a routine vet appointment, the Vet pointed out that these bumps were potentially Squamous Cell Carcinoma, which is actually a form of skin cancer that can be fatal to your horse...if left untreated.

I was a bit shocked and disappointed because for the last few years, I have taken precautions to make sure that he had a good UV protective fly mask on whenever he was out in the sunlight…all year round. Some at the barn questioned why the mask in the middle of winter and I explained that we were protecting his face and eyes from sun damage. Apparently, it was not enough.

Shortly after diagnosis and discussions with the vet, Rio was scheduled for surgery where the doctors were able to remove the bumps. They also found 2 additional bumps on the other eyelid and third eyelid which we hadn’t even seen.

Thankfully, we caught it early and got it treated, so the surgery and recover were fairly simple.

What is Squamous Cell Carcinoma (SCC)

Simply put, it’s a form a skin cancer.

According to Equimed.com, SCC tumors appear as solitary, raised, irregular masses, often ulcerated or infected, that develop around the eyelids (and third eyelids), genitals, face and ears, anal region, and other areas with minimal hair coverage and pigmentation. SCC tumors are slow-growing and are found most often in horses with white faces or markings that extend around the eyes.

According to Practicalhorsemanmag.com, as it grows, squamous cell carcinoma can begin to invade surrounding tissues, including the eye or even bone. It can also metastasize to other parts of the body. Growths around the eyes may spread first to the lymph nodes under the jaw. Once in the lymph system, the cancer can travel to other locations. It's the most common internal tumor in the intestinal tract, and the second most common overall.

Signs/Symptoms

On the skin, a squamous cell growth may look like a small sore or a red, raised bump. Small growths are often easy to spot when they appear around the eyes, where they're often on the inner rim of a lid or in the third eyelid (the membrane at the inner corner of the eye). Tumors in other spots, like the sheath, are more easily missed--look for red, raised sores and sometimes a foul odor.

Other symptoms may include:

• Small nodules
• Ulcerated areas with a foul odor
• Loss of appetite
• Weight loss
• Lethargy
• Abnormal chewing and swallowing behavior
• Anemia