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Feline Squamous Cell Carcinoma

by Andrea Jensen
Fall 2009


pic Squamous cell carcinoma (SCC) is a well known type of cancer that affects all mammalian species, including humans. Squamous cells make up the superficial layer of the skin and line hollow organs of the body (lungs, esophagus, stomach, intestines), as well as the mucosa of the mouth, conjunctiva, and genitalia. All of these areas are vulnerable to carcinogenic damage, although in most species the most commonly affected areas are those which are exposed to ultraviolet light. As such, it is not surprising that pink skin is more commonly affected than heavily pigmented skin and sunny climates increase the risk of cutaneous tumors substantially. In areas that are not exposed to sunlight, such as the lungs, air pollutants are implicated just as they are in humans. Interestingly, it has been estimated that 74% of dogs and cats with primary squamous cell carcinomas of the lung reside in urban environments, suggesting that air quality may be partially to blame.

Where do our feline patients tend to be affected? The most commonly affected areas in cats are the nasal planum, tips of the ears, and the oral mucosa (usually gums or under the tongue). Less common locations in cats are eyelids, tongue, feet, lungs, tonsils, stomach, vulva, and sinuses. White cats or cats with any pink skin on the face are in the highest risk group, and this is magnified in cats that sunbathe either outside or by a window. While the average age of onset is 12 years, outdoor cats in sunny climates often develop tumors at a much younger age, particularly if they are white. Additionally, cats of any color are at a four fold increased risk of developing oral tumors in households where cigarettes are smoked indoors.

A unique feature of SCC is that it tends to cause erosive to ulcerative lesions rather than proliferative, although it can occasionally look like a lump when the oral mucosa is affected due to secondary swelling. Ulcerations provide an opportunity for secondary infections, as well. The combination of infection and the spread of cancer cells makes this tumor type very locally invasive and can reach surprisingly deep into the tissue and bone within weeks of the first sign. Any non-healing wound should be seen by a veterinarian without delay. Additionally, since it is often difficult to get a good look inside a cat's mouth at home, any evidence of oral discomfort or odor should be seen by a veterinarian. A tumor in the gums or any other part of the mouth can cause similar behaviors as cats with dental disease and can cause festering ulcers that become infected and odiferous.

Oral SCC carries a very poor prognosis in cats. If it is caught very early and the location is optimal for removal, the prognosis is better. Tumors in the gums of the upper jaw are not as operable as those of the lower jaw, as it can be impossible to get wide enough margins without invading the sinuses. The same is true for tumors under the tongue. Tumors in the very front of the lower jaw are more easily removed, although often times a portion of the jaw is removed with it. Even if a tumor is caught early, located in the front of the lower jaw, and successfully surgically removed with wide margins, recurrence rate within one year is 38%. Many cats do very well after a mandibulectomy, and the majority of guardians report a high quality of life in spite of some challenges relearning to eat, drink, and groom. Overall, however, any SCC of the mouth is considered very, very bad news.

Cutaneous SCC of the nasal planum and ear tips carries a much better prognosis when treated early. Certainly, noticing non-healing sores on the face and scabs on the ears is much easier than finding oral ulcers in time for successful treatment. Since SCC tends to be locally invasive but does not often metastasize very quickly, removal of very small tumors is often curative. Removal of the ear tips is a minor procedure that doesn't cause any significant hardship on the patient or the owners, and is no different than the ear tipping that is commonly performed on TNR cats. Removal of the tip of the nose is slightly less comfortable for the patient, but if it is done before the tumor begins to invade beyond the epithelium it can also be a very minor procedure requiring only a stitch or two and a week to heal. However, with each and every week that ticks by without treatment, the probability of successful removal goes down exponentially. As the tumor spreads across the entire surface of the nose, the amount of healthy skin available to close while preserving an open airway goes down. Once the tumor spreads into the nasal cavity, it becomes completely inoperable.

As with any cancer, there are multiple treatment options available. Surgical excision or cryosurgery (freezing) are almost always indicated if the size and location makes it possible, but may be combined with other therapies for a multimodal approach. The highest success rates reported have been with surgical removal combined with radiation therapy. Radiation has also been successful alone on very shallow tumors, particularly on the nose where surgery may be tricky depending on the distribution of the malignant cells. Chemotherapy alone has never been successful, but combined with radiation has shown promising results in one study using mitoxantrone and radiation together. Several non-steroidal anti-inflammatory drugs (NSAIDS), such as peroxicam and meloxicam have been shown to slow the progression and spread of most carcinomas. Steroids are also sometimes given in anti-inflammatory doses, but generally not at the same time as NSAIDS due to gastrointestinal side effects. Finally, antibiotics are frequently given because of the high likelihood of secondary infections with SCC. Many antibiotics also have anti-inflammatory properties of their own, in addition to their bacteriocidal or bacteriostatic properties which provides a multimodal approach to inflammation when combined with NSAIDS.

Squamous cell carcinoma is never good news for a cat, but early detection and treatment can make all the difference. If a guardian notices a small wound on a cat's nose that doesn?t heal in a few days, or some rough edges on the ear pinnae, it should be checked out by a veterinarian within a week or two. A month or two could actually be too late with the rate at which some of these tumors can spread. Oral tumors are harder to catch early, but annual dental visits can be very helpful. For guardians that are able to brush their cat's teeth regularly, they may also have some success doing an oral exam at home every month. It cannot be stressed strongly enough that the only hope of long term remission is early intervention. Once SCC has time to invade surrounding tissues and bone, palliative care becomes the only option.


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