Is your horse at risk for Squamous Cell Carcinoma?
Posted May 03, 2018
Squamous Cell Carcinoma (SCC), a type of skin
cancer that commonly occurs on white-skinned areas of horses, can
be difficult to treat. That’s why Dr. Leslie Easterwood, a clinical
assistant professor at the Texas A&M College of Veterinary
Medicine & Biomedical Sciences, said early detection and
treatment are key.
SCC most commonly occurs at mucocutaneous junctions, such as the
eyes, nose, sheath, vulva, and rectal sphincter, Easterwood
Although SCC has some genetic predispositions, sun exposure can
also accelerate the disease.
Easterwood added that SCC also can develop if the horse has
prolonged liver disease or if the horse has had a thermal injury.
Long-term exposure to toxic plants may also increase the risk of
liver dysfunction, and thus lead to SCC on the affected white
Early SCC lesions look like ulcerated erosions of the skin or
sun burning. These lesions can develop into tumors and spread to
other areas of the body, including the lymph nodes and sinuses.
If you think your horse may be developing a SCC tumor, immediate
care is recommended, as treatment can be challenging.
“SCC tumors tend to enlarge and damage surrounding tissue,”
Easterwood said. “As the tumors enlarge, they invade larger areas,
and this makes removal more difficult. Eyelid lesions are
particularly important to catch and treat early so that we can
maintain enough eyelid tissue so that the horse will be able to
blink and lubricate the eye. In advanced cases, we sometimes have
to remove the eye, even though it is not effected by the tumor,
because we do not have enough functioning eyelid to maintain
lubrication of the globe.”
There are a variety of ways to treat SCC; the ideal treatment
for each case is based on many factors, such as the location of the
tumor and the risk of the tumor spreading, Easterwood said.
Surgery, chemotherapy, and cryotherapy are some of the traditional
Photodynamic Dye Therapy (PDT) has been used at the Texas
A&M Veterinary Medical Teaching Hospital (VMTH) and has shown
great promise for the treatment of SCC.
PDT involves the removal of most of the tumor and injecting dye
into the affected area. The dye is then activated by exposure to a
therapeutic light. This activation causes the release of molecules
that result in death of the remaining cancerous cells.
“To date, we have performed about 100 of PDT procedures at the
VMTH and have had overwhelmingly positive results,” Easterwood
There are also ways to help prevent SCC.
“Any decrease in sun exposure is likely helpful,” Easterwood
said. “Face masks with UV protection, SPF protective lotions, and
limited turnout during daylight hours are all ways to decrease SCC
Horses that have had SCC tumors in the past are more likely to
develop them again. It’s best to always keep an eye on your horse
and report any skin abnormalities to your veterinarian.
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