A typically alert and energetic cat that gradually or suddenly refuses to eat the food that you set out for it each day may be harboring severe discomfort somewhere within its oral cavity—the chamber leading from its lips to its throat. In most cases, the source of the problem will be a readily identifiable and treatable dental problem—periodontal disease, for example, that will quickly respond to therapy (possibly requiring the extraction of teeth adjacent to an irritating ulcer). Once treated, the patient can expect to enjoy a normal lifespan—given that its owners institute a strict program of dental care at home. However, the cause may also be the growth of an obtrusive and painful cancerous tumor—a condition that is likely to prove fatal unless promptly diagnosed and successfully treated.

According to Margaret McEntee, DVM, a professor of oncology at Cornell University’s College of Veterinary Medicine, oral cavity cancer is the fourth most commonly diagnosed type of feline cancer. Surpassed in frequency of occurrence only by lymphoma, skin cancer, and mammary cancer, oral cavity cancer accounts for about 15 percent to 20 percent of feline malignancies seen each year at the Cornell University Hospital for Animals. In addition to declining appetite—especially for hard food—the signs that an oral cavity tumor is present may include drooling, difficulty in swallowing, bad breath, facial swelling, red and swollen gums, and weight loss.

The vulnerable components of the oral cavity include the gums and lips, the hard and soft palates that make up the roof of the mouth, and the tongue. Of course, the oral cavity also contains the teeth, which are surrounded and supported by the periodontium, a normally sturdy structure that keeps the teeth anchored in the jawbone and protects them from the shock of chewing. All of these tissues, hard and soft alike, are potentially subject to the development of a tumor.

Three-fourths or more of oral tumors will be the result of a squamous cell carcinoma, a mass that develops on the internal surfaces of the mouth—in the tissues around the teeth, for example, or on the underside of the tongue. However, the tumors can also originate in nearby tissues, such as the salivary glands or tonsils. Other cancers that may invade the oral cavity, although much less frequently observed, include lymphoma, osteosarcoma, and melanoma. Overall, says Dr. McEntee, “Squamous cell tumors are the first thing we think of when examining a cat with a serious lesion in its mouth.” Other than the appearance of a growth in the mouth, one of the clearest signs of squamous cell carcinoma, she explains, is the inexplicably spontaneous loss of an intact tooth.

Unfortunately, notes Dr. McEntee, by the time most oral squamous cell carcinoma lesions are diagnosed via biopsy, they are too large for surgical resection and the cancer may have already spread to the animal’s regional lymph nodes. In that case, the prognosis is extremely unfavorable and treatment options include only “some form of palliative radiation and/or chemotherapy.”

Although not scientifically confirmed, it is widely believed that oral tumors may be caused by exposure to certain environmental carcinogens—especially tobacco smoke. This is a reasonable theory, notes Dr. McEntee, in view of the fact that cats groom themselves and ingest what’s on their coats. Associations have also been made with exposure to the chemicals in flea collars and to consumption of canned cat foods, especially those containing tuna. These associations, however, have not as yet been statistically confirmed.

Nevertheless, advises Dr. McEntee, owners might possibly reduce the risk of oral tumors by preventing a cat’s exposure to tobacco smoke, by consulting a veterinarian about the use of flea collars and the type of food it routinely consumes, and by paying careful attention to a cat’s oral hygiene. She urges owners to brush their cats’ teeth regularly (if possible) and to be aware of their oral hygiene in general. Routinely examine the animal’s face and oral cavity for any suspicious skin eruptions that might indicate the presence of a tumor.