Lung Cancer (Squamous Cell Carcinoma) in Dogs

The main function of your dog’s lungs is to provide good oxygen flow and pulmonary blood oxygenation to keep cells healthy. They do this by taking in oxygen from the air and exhaling extra carbon dioxide. When one or both of the lungs are affected by lung cancer, infection, or trauma, your dog’s life is in jeopardy due to inadequate lung function. Primary lung tumors are rare in dogs and only make up about 1% of cancer in dogs overall, but these numbers have been increasing rapidly in the past several years. However, out of the primary types of tumors in dogs (i.e. adenocarcinomas, bronchioloalveolar), squamous cell carcinoma is the least common and slowest to grow. 

Although this kind of cancer can affect breeds of any sex or age, it is seen most often in large breed dogs over the age of eight. The areas most often affected by the spread of squamous cell lung carcinoma are the lymph nodes, lobes of the lung, chest lining, bones, brain, and liver. Unfortunately, it is also the most deadly type of cancer, with extremely aggressive tendencies, so once it metastasizes (spreads) to the lymph nodes, it is difficult to stop. That is why it is extremely important to take your dog to the veterinarian if you suspect lung cancer of any kind.

Lung cancer in dogs can be primary (originating in the lung) or secondary (spread to the lung from somewhere else). Squamous cell carcinoma of the lungs is a slow-growing primary tumor of the tissue cells that is very aggressive. Squamous cells are found in the lining of blood vessels and organs in the body. Pulmonary squamous cells are flattened scales that make up the layers of the tissues inside the lungs.  Although this is a rare and slow-growing type of cancer in dogs, it has a high mortality rate because it is very aggressive.

The symptoms of squamous cell carcinoma of the lungs are varied and depend on the spread of the disease. If you catch it early, there may be no symptoms at all except maybe lethargy or weight loss, but the longer it has to spread, the more symptoms you will notice. Unfortunately, if you wait until you notice more than one symptom, your dog will not have a good chance of survival. That is why it is so important to bring your dog to the veterinarian at least once per year and right away if you see a change in your dog’s behavior or appetite. You know your dog better than anyone, so it is up to you to know when it is time for a trip to the veterinarian. Here are the symptoms that are most commonly noticed:

• Coughing
• Constant sneezing
• Difficulty breathing
• Weight loss
• Loss of appetite
• Limping (due to extra tissue growth in legs)
• Extreme sleepiness and weakness
• Blood in urine or stool
• Coughing up blood
• Not exercising

There are several causes of squamous cell carcinomas of the lung, but many times the cause is never discovered. Some of the most commonly suspected causes are:

• Age
• Exposure to chemicals
• Second-hand smoke
• Unknown

Those at the highest risk are large breed dogs (i.e. German Shepherds, Labrador Retrievers) eight years of age and older. Living with a smoker or exposure to toxic chemicals are also risk factors for squamous cell carcinomas.

For an accurate diagnosis, your veterinarian will need to know exactly what symptoms you had noticed and when they started. It is also important to note any recent trauma, illness, or changes in behavior or appetite. The veterinarian will do a complete and thorough physical examination, which includes vital signs (respirations, body temperature, heart rate, blood pressure), weight, and visual inspection of your dog’s eyes, ears, nose, and mouth. 

Tests that the veterinarian will need to do are blood work (CBC, blood gas, chemical panel) to check for an increase in white blood cells or a higher than normal level of calcium. Urinalysis, nasal and throat cultures, and radiographs (x-rays) of the chest, head, and abdomen. If the x-rays are not clear enough, your veterinarian will probably do an MRI, CT scan, or ultrasound for more detail. An endoscopy may also be done, which is a procedure the veterinarian performs to see inside your dog’s lungs without surgery. The endoscope is a long, skinny tube with a camera and tiny clipping device that will get a sample of fluids and tissues for examination. This will give a better view to see if lung cancer is present and will show the tumor or tumors inside your dog’s lungs. The endoscopy is minimally invasive and can be done in the office under local and general anesthesia. The risks are small, and the results are usually enough to give a definitive diagnosis.

Almost all dogs with squamous cell lung cancer need surgery to remove as much of the cancerous area as possible before starting any treatment, such as radiation therapy or chemotherapy. The surgery is called a lung lobectomy, which means they remove the lobe or part of your dog’s lung lobes affected by cancer. Your veterinarian may send you to see a veterinary oncologist to determine the best course of action for your dog.

After surgery, your dog will need cage rest with light activity (i.e. walk around the block, play catch for about 15 minutes) because he will be very weak and will need your help with eating and drinking. It is important to bring your dog to be checked at the first sign of lung cancer because waiting too long will most often be fatal. In fact, this illness has a high mortality rate even if you get your dog treatment because it is an aggressive cancer that is resistant to many medications.