Cancer in cats: symptoms, types and treatment

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 specialised care.

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Signs and symptoms 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 odours or discharges

• Increased thirst or urination

• Lameness

• Difficulty urinating or blood in the urine

• Vomiting

• Diarrhoea 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.

Common types of cancer in cats

Some cancers are more common in cats than others. 

Let’s look at six types of cancer that are most common in cats, some of the signs of cancer in cats and what pet parents should be aware of.

Lymphoma

By itself, lymphoma affects one in 2000 cats (48 per 100,000). 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 diarrhoea.

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 leukaemia 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.

2. Basal Cell Tumours

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

3. Mast Cell Tumours

Mast cell tumours 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 diarrhoea.

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

If a cat has just a few mast cell tumours 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 tumours tend to have the poorest prognosis because this form of the disease spreads quickly.

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

4. Squamous Cell Carcinomas

Squamous cell carcinomas (SCC) is a skin cancer in cats often located around the ears, nose, and eyelids, particularly in cats who are light in colour. 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 tumour will develop.

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

5. Mammary Gland Tumours

Ninety percent of mammary gland tumours in cats are malignant, but most cases are preventable when female cats are spayed before they are six months old. Mammary gland tumours 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 tumour is and if it has already spread at the time of diagnosis.

6. 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. You should still vaccinate your cat.

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 centimetres (3/4 of an inch) in size

• or growing bigger after 1 month

Treatment involves surgery to remove the tumour 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.

Diagnosing cancer in cats

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 specialised 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 specialise 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.

Treatment for cancer in cats

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 cat cancer treatment options 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:

Surgery

Surgery plays a big role in the treatment of many types of cancer. Sometimes one or more cancerous tumours 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 tumours are easier to remove, which increases the effectiveness of surgery and reduces the chances of complications during and after the procedure. Cats with large tumours 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!

Chemotherapy

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 tumour 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 tumour 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 anaesthetised 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.

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 final stages of cancer in cats, at a time when pet parents need to make informed decisions. Palliative care can include:

• Pain-relieving medications and pain management

• 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.

Quality of life is key for your cat

No matter how a cat’s cancer is treated, the primary focus always needs to be on their quality of life. Cat cancer symptoms vary, and care will look different for each cat.

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

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