Cancer in Pets: What You Need 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, while 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. Whether you have a new puppy or an old cat, it is so important to know and understand how cancer can affect their life before it is too late. The best treatment is prevention! 

If you have any immediate questions or concerns, please give our clinic a call. We are always on call for any emergency, so do not hesitate to reach out. Our number is (307) 347-2781, and you can also contact us here so we can help you the best we can!

The Basics

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. Due to the rapid cell increase, a majority of these cells become abnormal, which will then form a lump, called a tumor. Tumors, or neoplasm, are clumps of abnormal cells that continue to grow and divide with no control, causing damage to the body’s functions. 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. They are the building blocks for common cancers. 

If your animal tests positive for a tumor, know that the most common diagnosis is neoplasia. Neoplasia includes both benign and malignant tumors, so if you hear that word, do not jump right into cancer. No matter if your animal has a benign or malignant tumor, they still have a tumor that needs treatment.

Common Cancers

Please be aware that as we go through this list, your pet’s health is dependent on their genetics, lifestyle, and environment, and as such, risks and probabilities will vary. Consult a trusted veterinarian to assess your animal’s circumstances to give you a better idea of the concerns you should or should not have. Whether you’ve consulted a vet or not, there are two common cancers that you, a pet owner, should be aware of: lymphoma and osteosarcoma.


The most common type of cancer in both cats and dogs is lymphoma, especially in cats. Lymphoma targets the lymph nodes, which disrupts the animal’s immune system and blood cell count. Often, the tumors will go after the animal’s white blood cells, which are found in tissues and in the immune system. Animals carrying lymphoma can have it anywhere in their body, which contributes to the disease’s severity and aggression. 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 process.


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 bones and joints. Typically, it is found in the limbs, but the tumor is not exclusive to that area. Surrounding the affected bones, the related tissues, muscles, and organs can be very negatively affected. 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, swelling, 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 immediately if you have concerns about your pet’s health.

Cancer Causes

Because cancer is so varied from case to case, 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. If you have any questions or concerns, reach out to a trusted vet for answers.

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 prepares you for future health issues and can also inspire you to take prevention steps. 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. And in cats, the most susceptible breeds are Persians, Bengals, and Siamese. Knowing this information can really be a life saver later down the road.

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 the environment has 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.


As mammals age, their bodies become more prone to developing cancer, and pets are, unfortunately, no exception. Once animals reach a certain age, their immune system stops working so proactively and productively. As mentioned in the beginning of the blog, cancer is due to abnormal cells dividing so fast that they form tumors. Abnormal cells are a common occurrence in the body, however, our immune system will take care of these abnormalities before they become a problem. So, if an animal’s aging immune system is declining, their body will not be able to prevent the tumors.

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. When it comes to carcinogens, it is proven that their consumption can cause cancer in humans, so it is best to avoid them in pets altogether. If you are unsure, contact your vet.


There is no end-all cure for all cancers and all pets; cancer treatment is very individualized. With that being said, there are plenty of treatments available, including, chemotherapy, immunotherapy, radiation, surgery, cryosurgery and hyperthermia. The treatment that your animal receives is entirely dependent on them, their pain, and their health. A few things to consider when deciding the treatment plan are: age, cancer type, stage of cancer, and facilities. 

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 and all medical 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, so take the time to make the decision that is best for you and your family.  

It takes a village, so please lean on our Cloud Peak staff for support and advice. We want to help in any way possible, so please stop by our office if you have the time. If you have any questions or need a second opinion, give us a call at (307) 347-2781 and we will be more than happy to help you and your companion.



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