Squamous Cell Carcinoma

This disease is life-threatening and should be treated by a veterinarian swiftly.

Squamous cell carcinoma (SCC) is a locally invasive malignant tumour of the squamous epithelial cells.

It is characterized as a proliferative epithelial form of neoplasia and it generally shows up first in the skin, particularly around the eyes, on the penis or vulva, and in other areas where skin meets mucous membranes. Unpigmented skin has poor protection from the sun’s damaging UV rays, which are a factor in causing this cancer.

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. Once in the lymph system, the cancer can travel to other locations. It’s the most common internal tumour in the intestinal tract, and the second most common overall.

Symptoms

Common in

Treatment

Treatment options are determined by the size and location of the tumour. Smaller lesions are generally easier to treat. Unfortunately, many tumours are large by the time they are noticed, especially if they are located on the third eyelid, which can be difficult to see.
Surgery combined with follow-up treatment is the best option in many cases.

If the tumour can’t be surgically removed (it’s in a difficult place, for example), chemotherapy may be an option. The growths can be injected with a cytotoxic (cell-killing) drug such as cisplatin. Those around the sheath can be treated with a topical drug.

Squamous cell carcinoma also can be treated with radiation. In one method, radioactive “seeds” are implanted in the tumour and left in place for a few days to destroy the abnormal tissue.
Cryotherapy (freezing) is sometimes used for small external growths.

Prevention

Limiting exposure to ultraviolet radiation may help prevent squamous cell carcinomas, especially in horses with white or partially white coats.

Give horses with pink skin on the face or other areas extra protection from the sun, like fly masks. Turn them out at night and keep the horse stabled during hours of peak sunlight.
Clean a gelding’s sheath regularly; there’s some thought that a buildup of dirt and smegma contributes to cancer there.

Check light-skinned areas regularly and thoroughly to catch this cancer while it’s treatable.
Owners can use DNA testing to identify horses that are at higher risk for ocular SCC development and take precautions to protect them.