Squamous cell carcinoma (SCC) is the second most common type of skin cancer in horses, and one of the most frequent forms of cancer affecting the eye. 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.

Despite a large amount of research conducted on treatment for SCC, it is still a challenging condition to treat. The location of the tumor largely influences the type of treatment used. There are a wide range of currently available treatment options, however some are not universally accepted or supported by evidence based on clinical practice.