[Written by a Veterinarian] What is Feline Squamous Cell Carcinoma? Symptoms, Causes, Treatments, and Daily Care

"My cat has a growth in their mouth," or "I found a lump on their nose or ear"—these are signs that may point to a disease called feline squamous cell carcinoma (SCC). Because it often occurs in the mouth or on the skin and progresses rapidly, early detection is crucial. In this article, a veterinarian provides an easy-to-understand explanation of the symptoms, causes, treatments, and daily care for this condition.

What is feline squamous cell carcinoma?

Characteristics of squamous cell carcinoma (a malignant tumor of the skin and mucous membranes)

Squamous cells are the cells that form the skin and mucous membranes. Squamous cell carcinoma is a malignant tumor derived from these squamous cells. It is a common tumor in cats, particularly in the mouth, where it is said to account for 70–80% of oral tumors. Squamous cell carcinoma is characterized by its local invasiveness, meaning the tumor cells easily spread to surrounding tissues, while it is less likely to metastasize to distant organs.

Common sites for occurrence (mouth, nose, ears, skin)

Squamous cell carcinoma can occur in various places, including the skin, ears, nose, claws, and inside the mouth. Tumors in the mouth or jaw tend to grow quite large, leading to difficulties such as the inability to eat.

More common in older cats, but possible in younger ones

The average age of onset for squamous cell carcinoma is reported to be 14 years old, and it occurs most frequently in senior cats. However, it can also occur in younger cats, so being young does not mean they are safe.

Symptoms of feline squamous cell carcinoma

Growths, ulcers, and bleeding in the mouth

When squamous cell carcinoma occurs in the mouth, the initial signs may include redness, making it indistinguishable from gingivitis or stomatitis. As the tumor grows, it may develop into an ulcer, and eating may become painful. As the tumor continues to enlarge and occupy the oral cavity, the cat may be left with their tongue protruding, constant drooling, or the inability to close their mouth. The ulcers also worsen, leading to severe bad breath.

Increased bad breath and drooling

As the squamous cell carcinoma spreads, the tumor grows larger and ulcers form. If these ulcers develop a secondary bacterial infection, they may begin to discharge pus, leading to foul-smelling, cloudy drool. The bad breath will also become very pungent.

Lumps or sores on the nose or skin

When squamous cell carcinoma develops on the nose or jaw, it often forms a mass as it infiltrates the bone. As the tumor grows, it may cause fractures or distort the shape of the face.

Squamous cell carcinoma on the skin—often found on ears, noses, or paws—can cause the skin to suddenly become red and ulcerated. Scabs may also form, leading it to be mistaken for simple dermatitis, but a hallmark of squamous cell carcinoma is that the lesions continue to spread.

Loss of appetite and weight loss as it progresses

Squamous cell carcinoma progresses rapidly, and tumors in the mouth or jaw have a particular tendency to grow large. As the condition advances, the cat may struggle to chew or swallow, leading to a decrease in appetite and weight loss. Pain can also be severe, making eating difficult.

Causes and Risk Factors

Effects of UV radiation

While many aspects of the causes of feline squamous cell carcinoma remain unknown, it is believed to be influenced by exposure to ultraviolet (UV) radiation. The fact that it occurs in cats with white fur and on areas with lightly pigmented skin suggests a potential link to UV light.

Environmental risk factors

While the clear cause of squamous cell carcinoma remains unknown, some reports suggest that exposure to cigarette smoke or flea collars may increase the risk of its development.

Treatments and Prognosis

Surgery

If there is no metastasis, complete surgical resection is the primary treatment of choice. However, if the tumor is in the jaw, the jawbone may need to be removed, and in some cases, a portion of the tongue may also need to be excised. In such instances, since the cat may be unable to eat on its own, an esophageal or gastrostomy feeding tube will be placed to administer nutrition. Because the surgery can significantly change the cat's facial appearance, some owners may find it difficult to accept.

Surgery for oral or jaw squamous cell carcinoma is also performed as palliative care, with the goal of relieving pain and improving the cat's quality of life (QOL) rather than just attempting a cure.

Radiation and chemotherapy

If there is metastasis or the tumor cannot be completely removed through surgery, radiation or chemotherapy may be employed. Neither is curative; rather, the goal is to inhibit tumor growth and manage pain.

Prognosis according to the stage of progression

Feline squamous cell carcinoma progresses rapidly and is a highly locally invasive tumor that spreads to nearby tissues, even if distant metastasis is rare. Without treatment, the prognosis is generally about two months. If the tumor is completely removed by surgery, a survival time of one year or more can be hoped for. With palliative care alone, some reports indicate that the average survival time is not significantly different from cases with no treatment.

Daily Care and What Owners Can Do

Regular check-ups

In the early stages, squamous cell carcinoma in the mouth can be indistinguishable from gingivitis or stomatitis. Therefore, you should check your cat's mouth regularly and observe closely for any abnormalities. If it is difficult to check at home, have your veterinarian perform an examination.

Because squamous cell carcinoma progresses rapidly, even with treatment, the prognosis can be poor. As recurrence is also common, you must visit your veterinary clinic every few weeks to check for recurrence or metastasis to nearby lymph nodes. However, since abnormalities can appear even sooner, you should strive to check your cat at home every day.

Adjusting the diet

If a cat has oral squamous cell carcinoma, eating is often painful, making it difficult for them to get enough nutrients. Offering soft food that requires little chewing or serving soups may be beneficial.

If feeding via a tube becomes necessary, you will need to switch to a diet that won't clog the tube. Liquid diets are suitable for tube feeding. Tube feeding is not a quick process, so ensure you have enough time and patience to handle it calmly.

Tips for daily care

Squamous cell carcinoma often requires post-operative care. For example, if the jaw has been removed, not only is tube feeding necessary, but you will also need to manage constant drooling.

Check daily to see if the sutures holding the feeding tube in place are loose, if the thread has come off, if the tube has shifted, or if there is any abnormality in the skin where the tube is inserted. Disinfection may be required. When feeding through a tube, always verify that the tube is properly inserted into the stomach or esophagus before administering food. It is also necessary to flush the tube with water after feeding to prevent blockages.

Cats that have undergone jaw resection will experience constant drooling, which can lead to dermatitis on the skin affected by the saliva. Consider using a bib to prevent drool from contacting the skin and keep the area wiped clean.

Summary｜Facing a diagnosis of feline squamous cell carcinoma

Squamous cell carcinoma progresses rapidly and is often indistinguishable from other diseases in its early stages. You should suspect squamous cell carcinoma if you notice dermatitis, gingivitis, or stomatitis that is difficult to treat. Do not wait—consult your veterinarian immediately. Tumors in the mouth and jaw are common and tend to grow quite large, leading to symptoms like foul-smelling breath, heavy drooling, and loss of appetite. If you see these signs, seek medical attention right away.

Unfortunately, squamous cell carcinoma is a fast-moving, highly recurrent tumor. It may require extensive care. Please continue to shower your cat with love until the very end, and support them so that they can live the best life possible for as long as possible.