Oral squamous cell cancer is the most common type of oral cancer — in people and in pets. About 34,000 people in the United States are diagnosed with this cancer yearly. In dogs, oral tumors account for 70.4 cases per 100,000 dogs in the population. In cats, incidence rates are about 45.5 per 100,000.

The exact cause of oral squamous cell carcinoma is unknown. However, in people, smoking and drinking are major risk factors for developing this type of cancer. Heavy smokers who are also heavy drinkers are at a significantly increased risk.

Exposure to smoke may also be a risk factor for dogs and cats, although other environmental and genetic factors may also play a part.

Fortunately, oral squamous cell carcinoma has effective treatment options and the best survival odds when it’s detected and diagnosed early. In this article, we take a closer look at this type of cancer — including symptoms, treatment, and outlook — in people, cats, and dogs.

Oral squamous cell carcinoma starts inside the mouth. Nearly all mouth cancers are squamous cell cancers.

The cancer forms in the thin, flat cells that line the mouth. This type of cancer is sometimes called mouth cancer or oral cavity cancer. It’s one of several head and neck cancers that are often grouped together because they share overlapping symptoms and are treated with similar methods.

Oral squamous cell carcinoma causes lesions to form in the mouth. At first, these lesions might be present without causing any symptoms. When symptoms occur, they commonly include:

These symptoms aren’t always signs of oral squamous cell cancer. However, it’s always a good idea to make an appointment to get them checked out.

Even when these signs aren’t cancer, they can indicate gum disease or another oral infection. Additionally, earlier oral squamous cell carcinoma has a better outlook when it’s diagnosed and treated early.

Oral squamous cell carcinoma appears as flat red or white patches inside the mouth. You can see examples in the images below.

Humans aren’t the only ones susceptible to oral squamous cell carcinoma. This cancer also occurs in animals, including cats. When a cat has oral squamous cell carcinoma, you might notice symptoms such as:

  • bad breath
  • excessive saliva
  • weight loss
  • trouble eating
  • blood coming from the mouth
  • loose teeth

Oral squamous cell carcinoma in cats is treated with surgical removal of tumor growth, followed by radiation and chemotherapy.

Treatment can be very successful if the condition is caught early. However, oral squamous cell carcinoma can be very aggressive and spread quickly to bones and organs. Treatment can be difficult when this happens, and the outlook is often poor.

Dogs can also develop oral squamous cell carcinoma. Symptoms are similar to the ones pet owners might observe in cats and include:

  • bad breath
  • excessive saliva
  • excessive panting
  • trouble eating
  • blood coming from the mouth
  • reluctance to have head or mouth touched
  • frequent infections

Treatment follows the same model as oral squamous cell carcinoma treatment in cats. The first step is surgery to remove the tumor growth. And radiation and chemotherapy following surgery to kill the remaining cancer cells.

The outlook depends on how early the cancer is caught. With early treatment, oral squamous cell carcinoma in dogs can be treated successfully. However, treatment becomes significantly more difficult after the cancer spreads.

Researchers don’t know exactly what causes oral squamous cell carcinoma. It might be linked to genetic changes, but no specific genes have been found. However, there are several known risk factors for oral squamous cell carcinoma. These include:

Some studies have linked oral irritation and poor oral hygiene to an increased risk of oral squamous cell cancer. This link hasn’t been conclusively proven, but evidence suggests oral hygiene might play a role in both risk and survival odds.

Additionally, oral squamous cell carcinoma is more common in men than it is in women. However, it’s thought that this is because men are more likely to be heavier smokers and heavy drinkers, and not because biological sex on its own is a risk factor.

Sometimes, oral squamous cell carcinoma is diagnosed during a routine dental visit. Your dentist might spot a lesion and recommend testing to confirm cancer. In other cases, symptoms might prompt you to make an appointment with a dentist or doctor. In either case, you’ll need to have tests to confirm the diagnosis. These will include:

  • Imaging tests: You’ll have an X-ray, CT scan, or both so that doctors can get clear images of your head and neck. This can help them see the extent of the cancer.
  • Endoscopic tests: You’ll likely have both a laryngoscopy and an esophagoscopy. These tests use a small tool called an endoscope that allows a doctor to see the inside of your larynx and esophagus. This is done to rule out cancers in these areas.
  • Biopsy: A biopsy is the only way to confirm a diagnosis of oral squamous cell carcinoma. A biopsy is done by removing a small tissue sample from the lesion inside your mouth. This lesion is then tested in a lab.

The primary treatment for oral squamous cell carcinoma is surgery to remove the tumor lesion. Once the lesion is removed, radiation or chemoradiation is often done to kill any remaining cancer cells.

However, the exact type of surgery you need depends on the size and spread of the cancer. Additionally, further treatment options are available if chemotherapy and radiation aren’t effective. Full treatment options are discussed below.

  • Tumor removal surgery: Surgery to remove the tumor also requires the removal of some of the healthy tissue surrounding the tumor. If the tumor is very large, this might involve removing part of the lip, tongue, or jawbone.
  • Neck surgery: Sometimes, oral squamous cell surgery spreads to the lymph nodes in the neck. When this happens, you might have a procedure called neck dissection to remove the lymph nodes from your neck.
  • Radiation therapy: Radiation therapy kills cancer cells. It can be used alone or in combination with chemotherapy.
  • Chemotherapy: Chemotherapy is often combined with radiation therapy to help cancer kill cells.
  • Reconstructive surgery: Reconstructive surgery can involve restructuring your jaw, implants, dental bridges, and more to help restore the function and look of your mouth after tumor removal surgery.
  • Targeted therapy. Targeted therapy is a specialized kind of cancer treatment that works by blocking cancer cell growth. It can be an option when radiation and chemotherapy aren’t working.
  • Immunotherapy: Immunotherapy is a newer type of cancer treatment that teaches your immune system how to better find and kill cancer cells.

Since there isn’t a known cause of oral squamous cell carcinoma, there’s no guaranteed way to prevent it. However, there are ways to lower your risk. These include:

The outlook for oral squamous cell carcinoma varies depending on the stage at diagnosis, the location of the tumor lesion, the response to treatment, and on the individual’s overall health.

The table below lists the 5-year survival rate for oral squamous cell carcinoma on the lips, tongue, and lower floor of the mouth.

Location of oral squamous cell carcinoma5-year survival rate
oral squamous cell carcinoma of the lips91%
oral squamous cell carcinoma of the tongue68%
oral squamous cell carcinoma of the lower mouth floor 52%

It’s important to keep in mind that these numbers are based on data from 2011 to 2017. Treatments for oral squamous cell carcinoma have improved in the past several years.

This means that current survival rates are likely higher than the data reflects. Additionally, survival rates are much higher in the early stages no matter where the tumor lesion is located.

Oral squamous cell carcinoma is the most common type of oral cancer. It appears as a flat red or white lesion inside the mouth, on the tongue, and on the lips.

Oral squamous cell carcinoma can also develop in cats and dogs. In both animals and humans, early treatment significantly increases the odds of a successful outcome.

It’s important to have any suspicious lesions in your mouth checked by a dentist or doctor, or, in the case of your pet, a veterinarian.

Treatment includes surgery to remove the tumor lesion, along with radiation and chemotherapy to kill any remaining cancer cells. Sometimes, additional surgeries, including oral reconstructive surgeries, are also done.