Pet Care

7 Causes of Cancer in Cats

7 Causes of Cancer in Cats

Between cozy cat cuddles and play sessions with your cat's favorite feather toys, you do plenty to keep their health in tip-top shape, from feeding them quality, nutrient-rich food to ensuring they receive regular wellness exams.

That said, cancer is an all too common occurrence in cats and affects as many as one in five felines. Cats are also gifted at concealing their symptoms—and early detection is fundamental to getting them the care they need.

Fortunately, a grasp on what causes cancer in cats, coupled with the most telltale symptoms of the disease, puts you in a prime position to seek out prompt, high-quality veterinary care. Keep reading for the causes of cancer in cats and what you can do to prevent it.

What Is Cancer?

Before we slink into the subject, it may be useful to get a refresher on cancer itself.

Cells are an imperative part of an animal's (and humans') existence. Indeed, neither your cat nor you would be here without them. 

That said, cells regularly go through a process called cell division to generate fresh cells when the body requires them. At times, however, cells can multiply and grow uncontrollably. This may lead to growths that are either non-cancerous (benign) or cancerous. 

If left unchecked, the latter can spread throughout the body and wreak havoc on tissues and organs.

What Causes Cancer in Cats?

Several factors may heighten your cat's susceptibility to the disease.

1. Feline Leukemia Disease

As one of the most ubiquitous feline infections, Feline Leukemia Disease—or FeLV, as it's frequently called—impacts between 2% and 3% of cats in the nation and is widely known as the leading cause of cat cancer. 

How does it cause cancer? Feline Leukemia Disease suppresses the immune system, rendering cats more prone to infections and the development of cancerous cells.

Prevention tips

Approximately 85% of cats pass away within three years of a FeLV diagnosis. The good news? There are a handful of ways to keep your cat safe from contracting the infection in the first place.

  • Keep your cat indoors – Feline Leukemia virus is transmitted cat-to-cat, oftentimes through bites; it's also more widespread in outdoor cats, period. In fact, the only way to shield your cat completely from FeLV is to certify they don't come into contact with infected cats. 
  • Get your cat vaccinated – Since its release over 25 years ago, the FeLV vaccine has significantly reduced the rate of FeLV infections. The vaccine might not be an ironclad guarantee against FeLV, but it's an option you should discuss with your veterinarian. Bear in mind, however, that FeLV can be passed down to a kitten through an infected mother's milk. 

2. Secondhand—and Thirdhand—Smoke

The FDA reports that cats who live with a pet parent who smokes more than a pack of cigarettes per day are three times more likely to develop feline lymphoma—the most common cancer in cats.

It's not just a smoky environment that heightens the risk of cancer, either: Thirdhand smoke, or the residue from smoking, can cling to fabrics throughout your house, and cats love to nestle on sofas and nap on the carpet. Cats are also famous for their self-grooming behaviors, and toxic particles that are licked off their fur may result in oral tumors.

Prevention tips
Of all the causes of cancer in cats, this is one over which you have a great deal of control:

  • If you or someone in your household smokes, make sure they do so outside and away from your home's windows and doors. 
  • If you happen to move into a home that was occupied by a smoker, have the floors, walls, and any remaining furniture meticulously cleaned.

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3. Feline Immunodeficiency Virus

FIV in cats? Indeed. Feline Immunodeficiency Virus—or FIV—is one of the most widespread feline diseases, affecting approximately 2.5–5% of cats in North America. 

Although proper management of FIV may allow a cat to experience a standard, healthy life, FIV compromises the immune system and may make a cat substantially more vulnerable to cancer. 

Prevention tips

Presently, there is no vaccine for FIV. To shield your cat from contracting it, consider keeping them indoors. Additionally, you may want to think about the following:

  • Regular FIV testing – A cat with FIV can be asymptomatic for years and may put the other felines in your household at risk of infection, as FIV is typically spread through bite wounds. Have your cat tested for the disease when you adopt them, and ensure their status with regular FIV tests if they've been exposed to the infection and/or spend time outdoors.
  • Quarantining infected cats – Cornell University's College of Veterinary Medicine asserts that healthy and FIV-infected cats can live safely in the same household—and even share a water bowl and litter pan—if biting isn't a common occurrence. At the same time, you might reduce the risk of transmission by separating infected and non-infected cats.

4. Age of Getting Spayed

Mammary tumors are one of the most pervasive forms of tumors in cats, and mammary carcinoma goes down as the third most common type of feline cancer. Interestingly, a cat's mammary glands aren't localized to its breast area but extend across the belly from the groin to the armpit. 


Tumors can emerge anywhere in this area.

Prevention tips

Unfortunately, 85% of mammary tumors are malignant—but, like with all cancers, the earlier you receive a diagnosis, the more promising your cat's prognosis may be. To cut down your cat's risk:

Spay before one year of age – Cats who are spayed one year or older have a higher chance of developing mammary tumors. If you're adopting a female kitten, aim to have her spayed before five months of age. Doing so will also eliminate her risk of ovarian and uterine cancer.

Remain aware of your cat's specific risk factors – Cats ten years and older have a higher vulnerability to mammary tumors. The same goes for Siamese and domestic shorthair cats. But no matter your cat's age or breed, you should monitor their bodies for lumps and bumps and notify your veterinarian if you discover any cause for concern. 

5. Excessive Sun Exposure

Cats have a knack for designating the best spot of sun in a home as their own—and we'd have to say that a cat sleeping on a windowsill is one of the most iconic and heartwarming images in the world. 

And yet, cats are prone to skin cancer, particularly Siamese cats, breeds with pale coloring, and cats with patches of white fur. Excessive sun exposure can also cause solar dermatitis in kittens—a skin disease that may lead to skin cancer.

Prevention tips

Telling a cat to move out of a patch of sunlight is about as effective as commanding them to do… well, anything. (Who really rules the roost here?) But as your cat's parent, you can help protect them by:

  • Minimizing time outdoors – If you have an indoor/outdoor cat, make a concerted effort to bring them inside between the hours of 10 am and 4 pm. And if your cat adores sprawling out on your porch? Ensure it offers pockets of shade.
  • Installing UV-blocking window films – If you think closing the curtains might persuade your cat to nap elsewhere, think again: they may simply crawl underneath and take up their post on the windowsill. A more thorough approach is to implement UV-blocking films on your windows. 

6. A Poor Diet

The association between diet and the risk of cat cancer has not been thoroughly established. That said, a poor diet may be connected to the onset of lymphoma. It can also up your cat's chances of becoming malnourished, which may damage the liver and result in organ failure. 

Moreover, a cat who is given a nutritious diet, proper hydration, a low-stress home, and regular veterinary care may have greater vitality overall. 

Prevention tips

Making a few tweaks to your cat's diet is one of the simplest approaches you can take to improve their health. Give these a whirl:

Refrain from giving your cat a vegetarian diet – Cats are innate—or obligate—omnivores and should not be given a meat-free diet. Rather, they require nine essential amino acids that are present only in animal products.

Adjust your cat's diet throughout their life – Cats should have an optimal ratio of protein, fat, and carbohydrates, as well as water, vitamins, and minerals. Your cat's age, health status, and activity level will determine the right amount of each, so be sure to run their diet by your veterinarian and make necessary changes to their eating regime throughout their life.

7. Toxins

Few things top the cuteness of a curious kitten. But a cat's inquisitiveness may expose them to deleterious toxins, which may play a role in the development of hepatocellular carcinoma—a rare form of cancer that affects the tissues of a cat's liver.

Prevention tips

We baby-proof our homes for the children that come into our lives, and the same should be performed for cats. Specifically: 

  • Stash away medications – Human and veterinary drugs should be kept in a place to which your cat has zero access, even if he or she tries. Not only can toxins be what causes liver cancer in cats, but certain medications, such as NSAIDs, can be fatal for felines.
  • Eliminate exposure to chemicals and plants – Herbicides, incestides, household cleaners, and pesticides can all be toxic to cats. The same holds true for various plants, including lilies, oleander, and tulips.

What are the Symptoms of Cancer in Cats?

Cats are notorious for their independent streaks, and this may extend to how covert they are about their symptoms. Nonetheless, keep an eye out for the following:

  • Weight loss
  • Gastrointestinal issues like vomiting and diarrhea
  • Lack of appetite
  • Difficulty urinating
  • Extreme thirst
  • Lameness 
  • Foul odor and/or breath
  • Excessive drooling and salivating

Above all, step away from the internet to deny or confirm signs of cancer. You know your cat and their unique personality and way of life, and any changes in its behavior or health that gives you pause (or paws) are reason enough to consult with your veterinarian to know the types of cancer in cats and understand cancer in cats symptoms

Practice Cancer Prevention with Papaya Pet Veterinary Care

Cancer is an unfortunate possibility for cats. Thankfully, you can mitigate your cat's risk of developing the disease with a lifestyle that prioritizes wellness and there are options for surgery to remove feline cancer. 

Superior veterinary care is a large part of this—and Papaya makes it all the easier to obtain. We offer pet-first, ultra-welcoming animal clinics to help you stay on top of your cat's health, and also answer any questions like how to prevent cancer in dogs. Plus, our Fear Free practices will help your cat have a calm, nurturing experience.

Schedule a complimentary consultation with us today to learn more about our one-of-a-kind veterinary services.


  1. National Cancer Institute. What is cancer?
  2. PetMD. Cancer in cats: symptoms, types and treatment.
  3. Cornell University College of Veterinary Medicine. Feline leukemia virus.
  4. Morris Animal Foundation. Catching cancer in cats.
  5. U.S. Food & Drug Administration. Secondhand (and third-hand) smoke may be making your pet sick.
  6. VCA Animal Hospital. The effects of secondhand smoke on pets.
  7. PetMD. FIV in cats: symptoms, causes, and treatment. State University Veterinary Medical Center.
  8. Feline mammary tumors.
  9. Today's Veterinary Practice. Is there an optimal age for cat spay or neuter?
  10. PetMD. Solar dermatitis in cats: how to prevent cat sunburn.
  11. Fetch by WebMD. What do cats eat?
  12. PetMD. Do cats need high-protein cat food?
  13. Colorado State University Flint Animal Cancer Center. Common cancers in cats.
  14. PetMD. Liver cancer (hepatocellular carcinoma) in cats.
  15. University of Florida Small Animal Hospital College of Veterinary Medicine. Feline toxins and poisons.
  16. PetMD. Poisonous plants for cats.


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