Tonsil Cancer (Squamous Cell Carcinoma) in Dogs

Tonsillar squamous cell carcinoma begins in the squamous epithelium. The epithelium is a part of the four different types of animal tissue. There are three others, which are muscle tissue, connective tissue, and nervous tissue. In the epithelial cells, there are three shapes of other cells called cuboidal, columnar, and squamous. The glands in your dog’s body are made of these epithelial cells and their functions are to sense, transport, absorb, and secrete materials like blood and other cells. When one of these cancer cells show up in the squamous epithelium, it multiplies rapidly and spreads to other parts of your dog’s body, such as the bones, lungs, brain, and other vital organs. That is why it is so important to get treatment as early as possible, which can be difficult if the symptoms do not become evident until sufficient damage has already been done. The best way to avoid this from happening is with regular annual checkups at the veterinarian or clinic. The cause of tonsillar squamous cell carcinoma is (as is the case with most types of cancer) not known, but veterinary medical experts believe it has something to do with environmental pollution because it is much more common in cities than in rural areas. In addition, large breeds are more susceptible to tonsillar squamous cell carcinoma, and it is much more common in male dogs and those over the age of seven.

Although tonsil cancer (tonsillar squamous cell carcinoma) is an uncommon condition, it is the second most common oral tumor in dogs. As with many other cancers, tonsillar squamous cell carcinoma is classified as primary or secondary. Primary means that the cancer originated in the tonsils, and secondary means that the cancer has spread to the tonsils from another part of the body. Just like any other kind of cancer, the earlier it is found and treated, the better the chances for survival. However, the chances are high that the cancer will already have spread to the lungs through the lymph nodes. Whether the tonsillar squamous cell carcinoma is primary or secondary, this is a fast growing cancer and has a high (over 70%) metastatic rate, so the prognosis is usually not good.

Signs of tonsillar squamous cell carcinoma are usually not noticeable until the tumor is large enough to cause symptoms, or if it has spread to other parts of the body. In many cases, the tumor is found during a routine examination by a veterinarian, which is another reason it is good for your dog to see the veterinarian at least once per year. Some of the most common symptoms of tonsillar squamous cell carcinoma are:

• Cough
• More tired than usual
• Lump or swelling on face, neck, or inside the mouth
• Foul breath
• Drooling more than usual
• Blood tinged saliva
• Significant loss of weight
• Trouble eating and drinking
• Having a hard time swallowing
• Gasping for breath

Types

• Primary tonsillar squamous cell carcinoma originates in the tonsils
• Secondary tonsillar squamous cell carcinoma spreads from somewhere else in the body

The true cause of tonsillar squamous cell carcinoma is unknown, but these are some of the risk factors suggested by experts:

• Much more common in the city than in the country
• Large breed dogs are more frequently affected
• Almost all dogs with tonsillar squamous cell carcinoma are over seven years of age

The veterinarian will do a full body examination, paying special attention to your dog’s mouth and throat. He will measure your dog’s weight, blood pressure, body temperature, heart rate, and pulse oximetry to see how much oxygen is being circulated in the blood. At this time, it is a good idea to fill the veterinarian in on what has been going on with your dog, if there have been any episodes of strange behavior, any recent sickness or trauma, or changes in appetite. Once the physical examination is done, the veterinarian will run some diagnostic tests, such as a cytology test done by using a thin needle to extract some cells from the tumor or lymph nodes. Once the cells are extracted, they are examined microscopically to check for cancer cells. The veterinarian will also take some blood for CBC, blood gas, chemical analysis, clotting test, and glucose levels. Imaging with x-rays, MRI, CT scan, or ultrasound may be done as well, especially to determine if the cancer has spread. The CT scan is best for viewing the lungs because it is more sensitive and detailed.

The treatment for your dog’s tonsillar squamous cell carcinoma depends on how advanced it is, how far the cancer has spread, as well as the age and health of your dog. Surgery to remove the cancer and the surrounding tissue, bone, and lymph nodes is the best option if your dog is healthy and the cancer has not spread. However, it is important to remember that the average survival rate with this cancer is approximately four months, even with aggressive treatment. Radiation therapy is also recommended after surgery and for tumors that are unable to be removed surgically. This usually includes daily treatments of low doses of radiation. The side effects can be rough for some dogs, and may not be feasible if that occurs.

The survival rate with both treatments together is only six to eight months, with the tumors recurring in almost 100% of the cases. Sometimes the best choice is palliative care, to make your dog comfortable for the time he has left.