Thursday, February 25, 2021

Cats and Cancer

The dreaded Big C! One hates to hear of a loved one getting a diagnosis of cancer, but it can be even more heartbreaking when one of our cats receives the diagnosis. Cats are masters at hiding illnesses, so cancer can be harder to detect which may lead to later diagnoses and more difficult and costly treatments. Did you know that cancer afflicts an estimated 2% of the 80 million (2021) or more housecats now living in the United States? 

Cancer is a term that is used to describe a disease that is caused by a tumor, or neoplasm, that is a collection of abnormal cells within the body that can continue to grow and divide without control. This growth usually results in the development of masses. Some tumors do not spread to other parts of the body (benign) whereas others invade surrounding normal healthy tissue and may spread to other parts of the body (malignant). Recent data shows that 1 in 5 cats will be diagnosed with cancer in their lifetime. Dr. Dave Ruslander, veterinary oncologist and past president of the Veterinary Cancer Society, states that cancer in cats is at about half the rate veterinarians see in dogs and when they do see cancer in cats, it tends to be more aggressive.

Veterinarians don't really know what causes feline cancer. Some theories suggest it's genetics or environmental in nature. Cats are living longer, so veterinarians are seeing more cancers. Recent studies suggest secondhand smoke can contribute to cancer in cats. Exposure to sunlight, especially for light skinned cats, can lead to skin cancer on the ears and face. Some theories link feeding canned food, especially food that contains tuna may lead to some oral cancers. 

Tortoiseshell Persian Cat with Mast Cell Tumor beside nose
14-year old Persian cat with a Mast Cell Tumor on the side of her nose

Types of Feline Cancer

There are four main types of cancer that can be found in cats: Lymphoma, Squamous Cell Carcinoma, Mammary Carcinoma, and Fibrosarcoma. Other forms of cancer found in cats are Basal Cell, Mast Cell, and Leukemia. 


The most common type of cancer found in cats is Lymphoma. Lymphoma can be associated with the Feline Leukemia Virus (FeLV) and even though there is a vaccination for FeLV now, vets still see cats who've been exposed to it. Lymphoid tissue is normally located in many places in the body, including lymph nodes, spleen, liver, gastrointestinal tract, and bone marrow. Lymphoma of the digestive tract is the most common.

Squamous Cell Carcinoma

Squamous Cells are flat, irregularly-shaped, scale-like cells that constitute the outer layer of the epithelium and is usually identified as skin cancer.  Dr. Margaret McEntee, Cornell University College of Veterinary Medicine, states that skin tumors are the second most common type of feline cancer that is diagnosed at Cornell University. If the squamous cell is found in the mouth, they are known as Feline Oral Squamous Cell Carcinoma (FOSCC), and accounts for approximately three-fourths of of lesions found in the mouth of a cat. Squamous Cells are highly treatable if found early, but can be lethal if it goes unnoticed. 

Mammary Carcinoma

Mammary Carcinoma (breast cancer) is the 3rd most common type of cancer diagnosed in cats. Approximately 90% of mammary tumors found in cats are malignant and can be found in regional lymph nodes and lungs. Mammary cancer is mainly found in female cats and is most frequently diagnosed in cats that are older than 10 years old. The underlying cause of mammary cancer is still unknown, but veterinarians recommend having female cats spayed before they enter their first heat cycle, to offset the production of estrogen and progesterone. 


A Fibrosarcoma is a soft tissue sarcoma, which is a tumor that develops in the muscle or in the connective tissue of the body. A sarcoma is the type of tumor that is associated with injections and vaccinations and is sometimes called Injection-Site Sarcomas (ISS) or Vaccination Associated Sarcoma (VAS). Fibrosarcomas are rare and only occur in about 1% of felines as a result of injections or vaccinations. Fibrosarcomas can develop within a few weeks after a vaccination or injection or may take several years. These tumors tend to spread slowly and veterinarians can usually remove them, but they have a tendency to come back. Veterinarians now give vaccinations that are non-adjuvant because that is one theory for the formation of these tumors. Some veterinary researchers believe fibrosarcomas may be genetic in nature. Fibrosarcoma tumors have cancerous cells that extend invisibly outward, like fingers, into what appears to be healthy skin tissue and muscle.

small silver shaded persian kitten with an incision to remove a fibrosarcoma
11-week old Persian kitten recovering from surgery to remove a fibrosarcoma

Symptoms and Diagnosis

Early detection is the best way to catch cancer in the early stages where treatment and a longer quality life is possible. Regular wellness visits to your veterinarian will allow him to get baseline data through examination of the skin and mouth, blood work, and vaccinations where he can determine changes on subsequent visits. However, if you notice something unusual with your cat, take her to the vet for further examination. Some symptoms that may indicate cancer are:

  • External lumps and bumps
  • Excessive vomiting and diarrhea
  • Difficulty in breathing
  • Poor appetite
  • Weight loss
  • Rough coat
  • Lack of energy
  • Changes in the eyes
  • Unexplained bleeding
  • Wounds that won't heal
  • Dysphagia, halitosis, increased drool or oral discharge, or blood present in food or water

If your cat is presented with any of the above symptoms, your vet will begin by gathering a list of symptoms and when they occurred and will follow up with a physical examination of the stomach, skin, eyes, and mouth. If the veterinarian finds something suspicious, he may recommend the following diagnostic tools.

  • X-rays and ultrasounds. Can identify the location and extent of any tumor

  • Biopsy. Surgical removal of a small piece of affected tissue and allows a pathologist to tell the type of cancer

  • Fine needle aspiration. A small needle is inserted into a mass to remove a few cells that can be smeared on a slide for examination.

  • Blood samples. Can detect any adverse effects of the cancer and allows the veterinarian to detect the presence of other diseases.

  • Computed axial tomography (CAT or CT scan). Combines X-ray imaging and computer technology and is helpful in preparing animals for surgery and helps pinpoint specific areas of the feline anatomy that will be treated with radiation therapy.

  • Magnetic resonance imaging (MR scan). Used to diagnose brain tumors and to assess the extent of tumor invasion.

silver shaded Persian cat being examined by veterinarian
Taking your cat in for regular wellness checkups can help diagnose cancer and other illnesses early


Early evaluation, diagnosis, and appropriate treatment of cancer may result in significant improvement in the quality of life for affected cats and may extend their lives. The type of treatment that is used depends on the type of cancer, the site of the cancer, the presence of metastases, what is appropriate for your pet, and what is available/accessible to the owner.

  • Surgery. Surgery is used to completely remove the tumor or to partially remove the tumor to help improve the quality of life or to help with additional treatments. When surgery is performed, the veterinarian may also remove normal tissue around the tumor (surgical margins). Many tumors may contain abnormal cells in normal tissue and removal of the margins help to avoid future problems.
  • Chemotherapy. Drugs can be used for management of lymphoma and aggressive tumors that have spread to lymph nodes and other organs. Cats tend to tolerate chemotherapy well because lower doses are often used to avoid side effects that may affect the quality of life. Unfortunately, there are not as many advances in drug treatments for cancer in cats as there are for dogs because more dollars tend to go to dog cancers.
  • Radiation. Radiation is used in situations where tumors can be removed, specifically in the brain or nasal cavity. 
  • Veterinary Oncologist. Taking your cat to a veterinary oncologist allows the owner to be more aware of options available for treatment. A veterinary oncologist  is more aware of clinical trials or novel treatments that many veterinarians aren't aware of. 
  • Palliative care. Cats in advance stages of cancer need special treatment to help with nutritional needs, pain management, fluids, hygiene, and euthanasia. 


Cancer in Cats. August 17, 2018. International Cat Care. https://icatcare.org/advice/cancer-in-cats/

Eckstein, Sandy. April 9, 2012. Cancer in Cats: Types, Symptoms, Prevention, and Treatment.  Fetch by WebMD. https://pets.webmd.com/cats/guide/cancer-in-cats-types-symptoms-prevention-and-treatment#1

Hines, Ron, DVM, PhD. 2021. Vaccine Associated Fibrosarcoma Cancer in Your Cat and What You Can Do To Prevent It. Vet Space.  https://vetspace.2ndchance.info/cat-health-articles-table-of-contents/vaccine-associated-fibrosarcoma-cancer-in-your-cat/

Home Care for the Cancer Patient. Cornell Feline Health Center. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/home-care-cancer-patient

MacKenzie, Pellin, DVM and Turek, Michelle, DVM. 2020. A Review of Feline Oral Squamous Cell Carcinoma. Today’s Veterinary Practice. https://todaysveterinarypractice.com/feline-oral-squamous-cell-carcinoma/

Mingus, Lauren. November 20, 2019. Common Cancers in Cats. Colorado State University Flint Animal Cancer Center. https://www.csuanimalcancercenter.org/2019/11/20/common-cancers-in-cats/

Pellin, MacKenzie, DVM and Turek, Michelle, DVM. 2020.  A Review of Feline Oral Squamous Cell Carcinoma. Today’s Veterinary Practice. https://todaysveterinarypractice.com/feline-oral-squamous-cell-carcinoma/

Squamous Cell Cancer: Dangerous. Cornell Feline Health Canter. https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/squamous-cell-cancer-dangerous

Would you like to comment?

  1. Yes, cancer is really evil and we're sure praying for progress on the treatment front.

  2. Seeing any loved one go through cancer is a painful experience. I lost my beloved Luna to mammary carcinoma. My mom had two bouts of breast cancer, but was successfully treated and hoping that it never returns.

  3. I think more than 1 in 5 cats get cancer, but many don't take cats to the vet as they do dogs.

  4. Great post! Thank you for writing this. Awesome! Thank you

  5. Cancer sucks. Sadly I've had quite a few family members suffer through it. Years ago now I lost one of my house rabbits to lymphoma. With my current pets, I'm always on the lookout for anything unusual in hopes that, if they do ever come down with anything serious like cancer, I can catch it early and hopefully improve the outcome.

  6. Thank you for sharing this. I have researched and studied dog cancer for years and have been advocating awareness just as long. Depending on the type of cancer, the cause is usually narrowed down to something specific. But I haven’t done extensive research on cats. I’m seeing more and more kitty clients of mine being diagnosed with cancer and like you said, the vets don’t really seem to know the cause. This is very interesting!

  7. Cancer sucks. I am grateful, though, about all I've learned from Dr. Sue Ettinger; she puts things into perspective and changed my mind on many of my pet cancer preconceived notions.

  8. This is such valuable information!

  9. Our Sweetie, has a mammary lump, just diagnosed a few days ago.
    We are considering our options, but it's a sad state of affairs.

    1. We're so sorry to hear this. Our thoughts are with you.

  10. This is really good information. Thank you, Paula, for writing it all here!

  11. Thank you for sharing this, it's great information that every cat owner should be familiar with. The ability to identify early signs can make a significant difference in whether or not you catch a cancer early enough to be treated effectively. Growing up, our cat developed cancer on his tongue and it was unable to be removed. When it hit the point that he was no longer able to eat, we had to make the difficult decision. I still hope that some day they will find an effective cure for cancer.

  12. Early detection can make a huge difference for some kinds of cancer. I'll be sharing this with my cat loving friends and family.

  13. We really DO need to be proactive helping our cats in thse situations. We monitored Harvey's ear cancer until it reached a point his ear tips came off. Careful monitoring helped us give him the best care AND he looked cute as a 'fold' cat.

    Sadly this didn't work with Little 'Un she got bone caner which was so hard to diagnose.

  14. This is so informative, great detail. A cancer diagnosis in pets is so heartbreaking. I wish we could find the causes of all these cancers in both pets & humans.

  15. We hate ta be thankful for VETS sometimes, but they know about us better the Bein doctors, so we need them.

  16. I've been through the tumor thing with Bear twice ... first thinking he had a sarcoma (right after we started our blog - 8 inch incision down his back to get an adequate margin) and now the mouth incidence - which probably would've been squamous cell (two surgeries). With Bear's IBD diagnosis, I also worry about lymphoma. It's so hard to wait for a diagnosis - and heart-breaking to get it. I didn't remember that Praline had a mast cell tumor - though I certainly remembered about Beignet (having been in that situation ourselves - thinking that was the reality. I never forget how lucky we got).

  17. Thankfully I've never had to go through this. Lexy had a lump removed, but thankfully it was benign.

  18. excellent post, very informative. I'm wondering why the other
    specialists of this sector don't understand this.
    You must continue your writing. I'm confident, you
    have a huge readers' base already!

  19. My Siamese cousin, Oliver, went OTRB last year, 'cause it was found that he was real sick with tummy cancer. And his doggy housemate, Kenner, went OTRB not too long after with mouth cancer. They were a part of my extended family and I miss them.


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