Squamous Cell Carcinomas in Cats

What Are Squamous Cell Carcinomas in Cats?

Squamous cells are flat, sheet-like cells with an irregular shape that form on the outer layer of skin and line the body cavities and internal organs, including the mouth. Squamous cells are located throughout the entire body, including the nail beds.

Squamous cell carcinoma (SCC) is a type of skin cancer that occurs when these cells rapidly and abnormally divide in the skin or tissue lining, forming singular tumors that often initially appear like small scabs or sores. However, as the disease progresses, tumors become ulcerative (painful breaks that occur in the skin’s surface) and highly invasive (spreading into the surrounding, healthy tissues). Multiple tumors at one time are possible.

These tumors can form anywhere but are commonly found on the face in light-pigmented cats, including the tips of the ears, eyelids, lips, and the flat portion of the nose, and can also be present within the mouth (oral squamous cell carcinoma). It is rare for SCC to occur in the internal organs.

This type of skin cancer invades locally over time, and prompt diagnosis and treatment are needed for the best long-term prognosis. SCC also has the potential to metastasize (spread to other areas of the body), including regional lymph nodes, if untreated for too long.

Symptoms of Squamous Cell Carcinomas in Cats

Clinical signs and symptoms of SCC depend on the location of the tumor and vary widely:

• Cutaneous (skin):
  • Small scabs or sores, can be singular or multiple, and are found on the tips of the ears, eyelids, and lips
  • Ulceration of the flat portion of the nose
  • Associated itchiness, scratching, hair loss
• Oral (mouth):
  • Foul odor from the mouth
  • Red, inflamed gums
  • Bloody discharge, excess drooling
  • Weight loss
  • Poor appetite

Causes of Squamous Cell Carcinomas in Cats

While the exact cause of SCC is not fully known, both genetics and environmental factors are suspected to play a role.

Like humans, sunlight exposure and UV light can damage DNA and cause abnormal replication and division in squamous cells in cats, particularly in those with light pigmentation. Trauma to the skin, especially due to burns, can also damage squamous cells.

Dental disease and the presence of inflammation within the mouth is thought to precipitate oral SCC. Chronic periodontal disease and stomatitis (inflammatory disease of the mouth) in cats can have an underlying viral cause, including calicivirus.

Cats are excellent groomers and, although not confirmed, exposure to certain environmental contaminants on the hair coat—such as cigarette smoke and chemicals in flea collars—have also been suspected in cases of oral SCC.

How Veterinarians Diagnose Squamous Cell Carcinomas in Cats

Early detection is vital in cats with SCC. Scheduling routine physical exams for your pet allows your veterinarian to discover skin tumors when they are small and more easily treatable.

If suspected, SCC can be diagnosed by a procedure called a fine needle aspiration (FNA). A sterile needle is inserted into the tumor and a sample of the cells is retrieved using a syringe. Your veterinarian, or a veterinary pathologist, will then examine the cells under a microscope, a procedure known as cytology.

In some cases, especially if the results of the FNA were unclear, your veterinarian may recommend a biopsy of the tumor. A sample tissue from the tumor, or the entire tumor, can be excised and submitted for histopathology review by a veterinary pathologist. This will help determine how invasive the tumor is and if adequate surgical margins were obtained. Adequate surgical margins means that no cancer cells were present on the outer edges of the tissue when surgically removed. This is the main goal when excising a tumor to prevent recurrence of growth.

Depending on the location of the tumor, your veterinarian may recommend additional diagnostics to determine the stage of the cancer, including an imaging study (i.e., X-rays, ultrasound) and lab work (i.e., bloodwork, urinalysis). In cases of oral SCC, skull and dental X-rays may be helpful in determining how invasive the tumor is, and in detecting any spread to other areas such as the neck and chest.

Treatment of Squamous Cell Carcinomas in Cats

The recommended treatment protocol for SCC will depend on the location of the tumor (or tumors) and the invasive progression of the disease.

The best treatment option for cutaneous SCC is surgical removal. The prognosis is favorable if the entirety of the tumor can be removed. Cryosurgery (the use of extreme cold to destroy diseased tissue) can be performed if the tumor is small.

SCC in other areas of the body, where surgery has a less favorable outcome, may require a more extensive treatment protocol that includes radiation therapy. Tumors present on the nose are commonly treated this way. This procedure will likely require a referral to a veterinary oncologist (cancer specialist).

Oral SCC can be treated with a combination of surgery and radiation. However, these tumors must be addressed in the early stages for the most successful outcomes and, even then, an overall poor prognosis is possible.

Recovery and Management of Squamous Cell Carcinomas in Cats

It is important to follow your veterinarian’s instructions once your pet is discharged to return home. Your veterinarian will likely prescribe medications to help prevent negative side effects during recovery. Anti-nausea, appetite stimulants, and pain medications are common examples.

An E-collar (recovery cone) will likely be needed to prevent any self-trauma or injury to surgical sites during the post-operative healing process. It is also important to keep any surgical sites clean and dry and limit your pet’s activity for at least 10 to 14 days to prevent dehiscence (opening of the wound). If you have any concerns while your pet is recovering at home, promptly contact your veterinary clinic.

For a light-pigmented cat, it may be helpful to limit its time in the sun to prevent large amounts of UV exposure.

How Long Can a Cat Live with Squamous Cell Carcinoma?

If diagnosed in its early stages, most cats with cutaneous SCC will go on to live healthy, normal lives. Recurrence of cutaneous SCC can occur if poor or inadequate surgical margins are obtained.

Unfortunately, cats that develop SCC in other areas, such as the mouth, have a poor long-term prognosis. Typically, a one-year survival rate is less than 10%. Oral SCC tends to be diagnosed at a later stage in the disease process and is highly invasive.

Early detection is critical for the best long-term prognosis in your pet. If you notice any suspicious skin lesions on your pet’s face, or you’re concerned about any potential dental abnormalities (i.e., sore gums, bloody discharge, foul odor, etc.), please contact your veterinarian for an appointment as soon as possible.

Featured Image: iStock/Nastasic