The ManyPets Guide to Cancer Treatment in Cats

24 March 2022 - 10 min read

This article was written for the United States market and the advice provided may not be accurate for those in the United Kingdom.

According to the Animal Cancer Foundation, one in five cats will be diagnosed with cancer in their lifetimes. But there is good news! Cancer treatment for cats is much better than it used to be. It’s easier than ever to find the type of treatment your cat could benefit from most.

In this guide to treating cancer in cats, we’ll look at the types of cancer that most frequently affect cats, how cancer is diagnosed and treated, and how pet parents can afford such specialized care.

Cat looking out window

Warning Signs of Cancer in Cats

Cancer can be most effectively treated when it is diagnosed at an early stage and the right treatments are provided as quickly as possible. Make an appointment with your veterinarian if you notice anything unusual with your cat, including:

  • New lumps or bumps, especially if they grow or change rapidly

  • Abnormal patches of skin

  • Lethargy

  • Weakness affecting the whole body or just one part

  • Pain

  • Poor appetite

  • Unexplained weight loss

  • Unusual odors or discharges

  • Increased thirst or urination

  • Lameness

  • Difficulty urinating or blood in the urine

  • Vomiting

  • Diarrhea or constipation

  • Coughing, sneezing, or difficulty breathing

Of course, symptoms like these aren’t always associated with cancer, but it’s best to seek veterinary treatment for any potentially serious problem as soon as you can.

Cat on table

Common Types of Cancer in Cats

Some cancers are more common in cats than others. Let’s look at six types that pet parents should be aware of.


By itself, lymphoma accounts for up to 30% of all cancer diagnoses in cats. It is a cancer of lymphocytes (a type of white blood cell) and the tissues where they are commonly found. Lymphoma can affect the gastrointestinal tract, kidneys, lymph nodes, mediastinum (the area between the left and right lungs), and other parts of the body.

The symptoms of lymphoma in cats depend on where the disease is located. The intestinal form of the disease is most commonly associated with weight loss and vomiting or diarrhea. Increased thirst and urination are the first symptoms that often develop when the kidneys are affected. Mediastinal lymphoma is associated with difficulty breathing.

Any cat can get lymphoma, but those who are infected with the feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are at higher risk. The disease also seems to affect Siamese and related breeds more frequently, as well as cats who live with people who smoke cigarettes.

To diagnose lymphoma, a veterinarian will use a needle to take some cells from affected tissues or take a larger biopsy sample. A complete health workup including sending tissue samples to a pathologist, blood work, FeLV/FIV testing, a urinalysis, x-rays, and possibly bone marrow aspirates and other tests will help the veterinarian determine the cat’s prognosis and plan the most effective form of treatment.

Lymphoma is usually treated with chemotherapy. Some pet parents choose simple, inexpensive protocols that can be expected to provide their cats with several months of good quality of life. Others opt for more complicated and expensive protocols that can give them a couple of years of extra time with their feline friends.

Basal Cell Tumors

Basal cell tumors (also called cutaneous basilar epithelial neoplasms) are the most common type of skin cancer in cats and tend to be located around a cat’s head and neck. Thankfully, the vast majority of these tumors are benign and can be completely cured with surgery. Siamese, Himalayan, and Persian cats appear to be at the highest risk for basal cell tumors.

Mast Cell Tumors

Mast cell tumors are most often located in a cat’s skin but can also affect the spleen, liver, and intestinal tract. Pet parents may notice a lump or abnormal patch of the skin, which can be itchy. The internal forms of this cancer are commonly associated with weight loss, poor appetite, vomiting, or diarrhea.

To diagnose a mast cell tumor, a veterinarian will use a microscope to look at a sample of cells taken from the tumor. They may also recommend sending a biopsy to a pathologist to get more information.

If a cat has just a few mast cell tumors on the skin that can be completely removed with surgery, their prognosis is excellent. Removing a cat’s spleen will often give cats a year or so of good quality of life if that’s where their disease is located. Cats with intestinal mast cell tumors tend to have the poorest prognosis because this form of the disease spreads quickly.

Any cat can be diagnosed with a mast cell tumor, but Siamese appear to be at higher than average risk.

Squamous Cell Carcinomas

Squamous cell carcinomas (SCC) are often located around the ears, nose, and eyelids, particularly in cats who are light in color. These areas aren’t thickly covered in fur and are poorly protected against the cancer-causing effects of the sun. Early on, SCC may just look like a small, scabbed-over wound that doesn’t heal, but eventually, a tumor will develop.

SCC can also be found in a cat’s mouth, where it often causes symptoms like drooling, bad breath, or difficulty eating. In fact, SCC is the most common form of oral tumor in cats.

A biopsy is usually needed to definitively diagnose SCC in cats. While this type of cancer rarely spreads to distant parts of the body, it is still very dangerous because it tends to invade deeper tissues very aggressively.

Surgery to remove as much of the tumor as possible is the first step in treatment. In the mouth, this may require the removal of part of the jawbone. Radiotherapy can also be very helpful, particularly in combination with surgery. If surgery can completely remove SCC in the skin, the cat’s prognosis is excellent. Unfortunately, most cats with SCC of the mouth only live for several months after treatment.

Mammary Gland Tumors

Ninety percent of mammary gland tumors in cats are malignant, but most cases are preventable when female cats are spayed before they are six months old. Mammary gland tumors can also occur in male cats, but they are rare.

Pet parents will often first notice one or more lumps in their cat’s mammary chain. A veterinarian will take a sample of tissue and perform a complete health workup to determine if the lumps are indeed cancerous and then make a plan of action. Treatment involves surgically removing the masses. Oftentimes it’s best to remove the whole affected mammary chain. Additional treatment can include chemotherapy and radiation therapy. A cat’s prognosis depends on how big the mammary gland tumor is and if it has already spread at the time of diagnosis.

Injection-Site Sarcomas

While injection-site sarcomas (ISS) do not occur as frequently as they used to, pet parents should still be aware that they can occur. Fibrosarcomas are the most common type of ISS. They are locally aggressive but usually don’t spread to distant parts of the body until late in the course of the disease.

Any injection can lead to ISS in cats, but certain types of rabies, feline distemper, and FeLV vaccines have been involved in most cases. Keep in mind, however, that the incidence of ISS after vaccination is very low—1 case per 10,000 to 30,000 vaccinations.

Use the 3-2-1 rule to help you determine if you should be concerned about a lump that develops at the site of an injection. Talk to your veterinarian if the lump is:

  • till there 3 months after the vaccination

  • 2 centimeters (3/4 of an inch) in size

  • or growing bigger after 1 month

Treatment involves surgery to remove the tumor and as much surrounding tissue as possible, often followed by chemotherapy and possibly radiation therapy to slow the cancer’s return. With this type of treatment, cats will often survive for a year or two after diagnosis.

Cat with veterinarian


An accurate diagnosis is essential before a veterinarian can give you an idea of what treatment options might be best for your cat and how effective they could be. This process starts with a thorough health history followed by a complete physical examination. However, there isn’t a single type of cancer that can be accurately diagnosed without some laboratory testing.

  • Veterinarians often begin by using a needle to collect a small sample of cells from a lump or bump and then look at it under the microscope.

  • Basic blood work combined with a urinalysis is a simple way to evaluate a cat’s overall health and how their internal organs are functioning.

  • FeLV/FIV testing is included in most feline health workups to determine if these viral infections are an underlying cause for a cat’s symptoms

  • X-rays and ultrasounds are widely-available, noninvasive ways to look inside a cat’s body.

  • Other diagnostic methods to detect cancer or determine how far it has spread can include endoscopy, CT scans, MRIs, and specialized laboratory tests.

In many cases, the veterinarian will want to biopsy (surgically remove a piece) of the abnormal tissue and send it off to a pathologist for review. Pathologists who specialize in cancer can confirm the diagnosis and often provide more detailed information that will be used to guide treatment.

The best combination of diagnostic tests depends on a cat’s symptoms and what types of cancer are most likely based on the specifics of their case.

Cat at vet's office


Every cat with cancer deserves treatment, but the right form will depend on many variables including the cat’s overall health and age, how advanced or aggressive the cancer is, and their caretaker’s desires and financial constraints. Because there are so many new and advanced cancer treatments available, your veterinarian may recommend referring you to a veterinary oncologist or other specialists.

The following options can be used alone or in combination to help cats with cancer.

Palliative Care and Euthanasia

In extreme cases, immediate euthanasia may be in a cat’s best interests. If suffering can’t be adequately controlled and treatment is unlikely to provide much in the way of benefit, helping a cat to pass peacefully can be a gift.

However, palliative care — treatments aimed at improving a cat’s quality of life, not directly addressing the underlying disease — can often make a cat comfortable during the time that pet parents need to make informed decisions. Palliative care can include:

  • Pain-relieving medications

  • Nutritional support

  • Fluid therapy

  • Assistance with urination and defecation

  • Keeping pets clean and well-groomed

  • Helping pets move around safely

  • Maintaining engagement with family life

  • Symptom management

Palliative care should always be integrated into euthanasia decisions and the forms of treatment used to directly fight a cat’s cancer.


Surgery plays a big role in the treatment of many types of cancer. Sometimes one or more cancerous tumors can be completely removed with surgery and no further treatment is necessary. At other times, surgery can significantly reduce the amount of cancer in a cat’s body, which has a positive effect on their quality of life and for other forms of treatment.

Small tumors are easier to remove, which increases the effectiveness of surgery and reduces the chances of complications during and after the procedure. Cats with large tumors may first need other treatments — like chemotherapy or radiation therapy — to shrink the mass and make surgery as safe and effective as possible. Don’t wait to get your pet checked out by a veterinarian if you notice something unusual!


Pet parents tend to have an understandably negative reaction to the thought of putting their cat through chemotherapy, but it’s important to remember that the word chemotherapy can mean many different things. Some chemotherapy drugs are very safe while others do have potentially serious side effects associated with them. However, veterinarians often treat cancer less aggressively than human medical doctors do, which lessens the risk and severity of side effects like bone marrow suppression or vomiting.

There are many situations where chemotherapy can be an essential part of cancer treatment in cats, including:

  • When cancer has originated in or spread to multiple parts of the body

  • When a cat has an aggressive type of cancer that has probably already spread

  • When other forms of treatment, like surgery, might be too dangerous for the cat or are unlikely to have a significant positive effect on the cat’s quality of life

  • To shrink a tumor before surgery or other forms of treatment

Different chemotherapy drugs are administered in different ways — orally, intravenously, intramuscularly, topically, subcutaneously, or even directly into a tumor or body cavity. In other words, you have choices! If you don’t want to bring your cat to the clinic frequently, perhaps an oral form of chemotherapy that you can give at home is available.

Radiation Therapy

Radiation therapy is most often used for cancers that are in locations where surgery would be very difficult or would lead to unacceptable outcomes. It can also shrink a mass before it is surgically removed or kill cancer cells that have been left behind after surgery. Sometimes the primary goal of radiation therapy is pain relief.

Most veterinary schools and some veterinary specialty practices can provide radiation therapy for cats. Protocols vary depending on the cancer involved and the goals of treatment. Typically, cats are treated anywhere from daily to once a week for around three to four weeks. They will need to be anesthetized during the procedure so they don’t move.

Emerging Forms of Treatment

New cancer treatments for cats are quickly being developed. Immunotherapy is a great example. For example, a vaccine is currently being tested that will hopefully help a cat’s immune system better fight fibrosarcoma. Novel gene therapies are also in development. The American Veterinary Medical Association maintains a searchable database of clinical trials that are looking into new forms of treatment for a variety of diseases.

Complementary Care

Everything we’ve touched upon so far in this article falls under the heading of “traditional” veterinary medicine, but complementary care can also be beneficial, particularly when used in combination with rather than instead of traditional techniques like surgery or chemotherapy. This combined approach to veterinary medicine is often called integrative or holistic care. Examples of potentially useful forms of complementary cancer treatment in cats include:

  • Acupuncture

  • Some herbal therapies

  • Nutritional intervention and supplements

  • Physical therapy

To avoid complications, always make sure your cat’s entire healthcare team is aware of all the treatments your cat is receiving.

Cat playing in a box

Quality of Life Is Key

No matter how a cat’s cancer is treated, the primary focus always needs to be on their quality of life. A short-term compromise may be necessary to achieve a long-term gain, but when a cat is suffering and there is no reasonable expectation that their quality of life will improve with continued treatment (including an increased level of palliative care), euthanasia may be the best thing you can do for your cat. Talk to your veterinarian about your options if your cat is experiencing significant and consistent decreases in their ability to:

  • Eat and drink

  • Urinate and defecate

  • Move safely around their environment

  • Experience some joy each day

Cats sitting at window

The Elephant in the Room: Cost

We haven’t yet touched on one important aspect of cancer treatment in cats — cost. There’s no way around it, treating cancer can be very expensive, but of course, there is a huge range depending on the specifics of a cat’s case. For example, cats with lymphoma can be treated with prednisolone, a form of chemotherapy that only costs a few cents per pill. Their symptoms will generally go into remission for a month or two after which time euthanasia often becomes necessary. On the other hand, cats with gastrointestinal lymphoma who receive more advanced treatments may enjoy remissions that last for two or three years but cost thousands of dollars before all is said and done.

Bills in the range of $3,000 to $7,000 are common for cancer treatment in cats, and some go even higher.

Costs like these can simply be unrealistic for many pet parents, which leads people to choose euthanasia when they would much prefer to pursue treatment. These “economic euthanasias” are truly heartbreaking, but there is another option.

Purchasing cat insurance (before your pet is sick!) will allow you to make decisions about your cat’s treatment without having to worry about its cost.

Jennifer Coates, DVM
Veterinarian, Veterinary Writer, Editor, and Consultant

Dr. Jennifer Coates is a writer, editor, and consultant with experience in veterinary medicine, science, animal welfare, conservation, and communications. She has written for outlets including petMD, Chewy, and ManyPets.