Pet Cancer: What to Know

Unfortunately, cancer in pets is just as common as it is in people. In fact, one in four dogs will be diagnosed with some form of cancer in their lifetime. One in five cats will be affected. While many other pet species can get cancer, dogs and cats are more likely to get it than any other animal. If you own either species, please continue reading to gain a little more knowledge on what you should be looking for. If you have any questions about your specific breed or species, contact us and we will help you the best we can!

Let’s start at the beginning with what cancer is and how it can manifest in your pet. In all types of cancer, some of the body’s cells begin to divide without stopping, and then spread into other tissues. These abnormal cells usually form a lump called a tumor. Tumors, or neoplasm, are clumps of abnormal cells that continue to grow and divide with no control.  Under the umbrella of tumors, there are two types: benign and malignant.

  • Benign tumors are not cancerous, and are contained in a specific area of the body. They do not generally infect other areas than where they began.
  • Malignant tumors are cancerous; these tumors are very active and will invade healthy tissue and continue to grow and divide at a very rapid pace.

Animals that develop either type of tumor often are diagnosed with neoplasia. Bottom line: any tumor will need treatment as soon as possible so that not all healthy tissue is destroyed. Malignant tumors are the building blocks of common cancers.

Common Cancers

Although the risks and probabilities of your specific pet getting cancer varies based on your specific situation, there are two common cancers that you should be aware of: lymphoma and osteosarcoma.


The most common type of cancer in both cats and dogs is lymphoma. Lymphoma is more common in cats than dogs, but dogs are at risk as well. It targets white blood cells, which are found in tissue and in the immune system. Animals carrying lymphoma can have it anywhere in their body. This is a very serious and very aggressive cancer. Lymphoma is tricky because its symptoms can vary dog to dog and cat to cat. With mild symptoms, your pet may experience a loss of appetite or fatigue. In more aggressive cases, your pet may experience weight loss, vomiting, diarrhea and weakness. The symptoms are very much dependent on where the lymphoma is, and which organs are being affected. When diagnosed early, and treated quickly and effectively, most dogs will go into remission. Most cats will have a very long-lasting treatment.


Another very common type of cancer is osteosarcoma, commonly known as bone cancer. Osteosarcoma is more common in dogs than cats. This type of cancer is extremely painful, as the tumor attacks an animal’s skeleton. Typically, it is found in the limbs, but the tumor is not exclusive to that area. The tumor can even affect the organs surrounding the bones. Signs of osteosarcoma are not definite, but typically, the bone will swell, causing severe pain. The bones will also become very weak and could lead to breaks or fractures. Immediately seek advice from your vet if you notice any lameness or abnormal walking.

While lymphoma and osteosarcoma are the two most common types of cancer in dogs and cats, there are many other different types that could affect your furry family member. Consult your vet if you have concerns about your pet’s health.

Cancer Causes

Please keep in mind that there are multiple possibilities when it comes to what causes cancer, and often no certainty. The section below simply addresses possible causes, not definitive ones.

Family Genetics

As you begin your search for a family pet, find out as much as you can about its family health history. Doing so enables you to be aware of possible health issues and concerns.  Breed type also plays a factor in whether your pet has a genetic predisposition for cancer, as some breeds are more prone to getting it in their lifetime than others. In dogs, German Shepherd, Great Danes, Golden Retrievers, Bernese Mountain Dogs and Rottweilers are among the breeds having a higher incidence rate of cancer than other breeds.

Environmental Factors

Along with genetics, the scientific community has a strong belief that there are environmental factors that can increase the likelihood of developing cancer. That belief comes from research done on humans and the impact of the environment on cancer patients. When animals are exposed to the sun’s UV rays for extended periods of time, there is an increased likelihood of cancerous tumors developing. Second-hand tobacco smoke is also a risk factor. With pets typically being outside, be aware of the pesticides and insecticides you use on your crops and gardens, as there are certain types and brands of these that can cause cancer. If you aren’t sure, be sure to contact your vet for help deciding on what would be best for you and your situation.


Keep in mind that as your pets age, they could be more prone to cancer. This is due to how cancer develops. As mentioned at the beginning of this article, cancer is a clump of abnormal cells that is dividing and growing without being stopped. What should stop these tumors, the animal’s immune system, weakens with age, so these tumors have less resistance in spreading.

Viruses and Carcinogens

Lastly, some viruses and carcinogens are suspected to cause cancer. Whenever your pet contracts a virus, discuss the likelihood of it causing cancer with your vet, as each case is different and specific to your pet.


There is no end-all treatment for all cancers and all pets; cancer treatment is very individualized. With that being said, there are plenty of treatments available, such as chemotherapy, immunotherapy, radiation, surgery, cryosurgery and hyperthermia. Which treatment to consider is entirely dependent on your pet:  what stage the specific cancer is in; how old they are; what kind of cancer that needs to be treated, and so on. When discussing treatments with your vet, make sure they have any medical and family history information that they may need to decide what course of treatment would be best.  Know that there are some instances when the most humane and loving decision is euthanasia. But again, treatment is very much dependent on your situation.

If you have any questions or concerns, or need a second opinion, give us a call and we will be more than happy to help you and your companion any way we can.



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