When cats suddenly or gradually refuse to eat their food, its possible that dental disease could be the reason, with mouth cancer being one of the more serious dental problems. According to Cornell Feline Health Center, oral cavity cancer is the fourth most commonly diagnosed cancer in cats. There are many different types of mouth cancer in cats, and some are more common than others.
An important part of pet parenthood is understanding how to support your furry friend's health. Read on to learn the signs of cat mouth cancer, the available treatment options and how to reduce your cat's risk of developing it.
What Causes Mouth Cancer in Cats?
The cause of mouth cancer in cats is still largely unknown. Oral squamous cell carcinoma (SCC), the most common mouth cancer found in cats, may have a viral cause. The scientific community at Today's Veterinary Practice also largely believes SCC can be caused by exposure to environmental carcinogens, such as chemicals in flea collars, consumption of canned tuna and secondhand smoke from cigarettes. A study in the Journal of Veterinary Dentistry showed that cats who wore flea collars had an increased risk of developing mouth cancer.
In addition, any chronic inflammation or irritation in the mouth, such as inflammation associated with dental disease, increases the risk of mouth cancer.

What Are the Types of Mouth Cancer in Cats?
The most common mouth cancer in cats is SCC, accounting for 70% to 80% of all cat mouth cancer. SCC creates a tumor in the mouth either in the tissues surrounding a tooth, on the underside of the tongue, on the roof of the mouth, on the tonsils or on the salivary glands.
The second most common type of oral cancer in cats, fibrosarcoma, destroys gums, bones and muscles in the mouth. Other types of feline mouth cancer include lymphoma, melanoma and osteosarcoma. These types of cancer spread from other parts of the body and are much less common than SCC or fibrosarcoma.
What Are the Signs of Cat Mouth Cancer?
In some cases, you or your veterinarian may be able to see a tumor in your cat's mouth. Other times, the signs are more subtle, and sometimes there are no signs at all. Mouth cancer can also mimic the signs of dental disease.
Some of the signs associated with feline mouth cancer include:
- Sudden loss of an apparently healthy tooth (seen in SCC)
- Bloody saliva that's red or pink-tinged
- Unexplained drooling
- Picky or decreased appetite, leaving food in the bowl or only eating soft food
- Dropping food when eating
- Plaque and tartar buildup on only one side of the mouth
- Weight loss
- Halitosis (bad breath)
- Pulling away or not allowing their head to be touched
- Swelling on one side of the face
How Is Cat Mouth Cancer Diagnosed?
If you suspect mouth cancer or any oral disease in your cat, schedule an appointment with your vet as soon as possible. They'll conduct a full physical examination and may need to sedate your cat to examine their mouth and take X-rays. Your vet may also order other tests, including bloodwork and a biopsy of any masses within the mouth to determine if it is cancer. More rarely, they may recommend an MRI or CT scan.