Squamous cell carcinoma is a tumor that originates from squamous cells. Squamous cells form the surface layer of many tissues throughout the body, including the cornea, conjunctiva and eyelid. Because squamous cells are located on the surface of these tissues, they are exposed to UV light. This exposure may result in damage, mutation, and eventually cancerous transformation of these cells.
Squamous cell carcinoma is a common tumor of horses in areas of intense sunlight or high altitude. It is one of the most common tumors of the eye of the horse. Non-pigmented skin and membranes are especially susceptible to the development of this tumor, which may involve the eyelids, conjunctivaor cornea. Appaloosas, color-dilute breeds and draft breeds are particularly susceptible to development of this tumor. Squamous cell carcinomas may initially appear as a red roughened or ulcerated area. The tumor soon develops into a small pink or red mas. These masses are lumpy, irregular and frequently ulcerated. If left untreated, the mass may enlarge and spread around and behind the eye, to sinuses, bone, brain oreven other parts of the body. Squamous cell carcinoma can be diagnosed even in its earliest stages by a biopsy performed by the veterinary ophthalmologist. Treatment of squamous cell carcinoma varies with the location, size and the extent of the tumor. Treatments may involve surgical removal, freezing or heating, local radiation, local chemotherapyor removal by laser. Despite the type of treatment used there is a potential for recurrence of the tumor and additional treatments may be required. The prognosis for horses with squamous cell carcinoma is usually good if the tumor is small and involves only a small part of the globe or third eyelid. If the tumor is large and extensive or involves the upper or lower eyelids or the space behind the eye the prognosis may be poor.
The following practices may decrease your horse’s risk of squamous cell carcinoma: avoiding the sun between 10:00 a.m. and 3:00 p.m., providing protection of the eyes from insects, dust and wind (for example: with facial nets or fringe), using sunscreens and tattooing non-pigmented skin.
If you have any further questions about squamous cell carcinoma, please call Eye Care for Animals.
