Cancer in Cats: Early Diagnosis Gives the Best Prognosis

The term cancer in cats often strikes terror to our hearts in the same way it does to a person when they hear the word “cancer” regarding their own health or that of a loved one. As much as treatments have improved and cures have been found and lives have been extended, we still hate the word.

This is true in veterinary medicine as well. I’d much rather diagnose hyperthyroidism in cats or cat diabetes or feline kidney disease than to have to tell a pet owner that their best cat friend has feline cancer.

What is cancer?

In the most simple terms, cancer occurs when normal cells become abnormal and they divide and thus replicate in an uncontrolled manner.

Any cell can become this way – that is why we have so many different types of cancer. For every cell type you have in your body – liver cells, skin cells, brain cells, muscle cells, kidney cells, and on and on – that type of cancer can develop.

Cats are no different. They have pretty much the same organs and cell types we have so it should come as no surprise that they can develop the same types of cancer that occur in man. Their organs, bones, and blood cells can develop abnormal cells just as ours do. A cat can have feline lymphoma, a feline mammary tumor, cat skin cancer, feline bone cancer, or one of many other cancer types.

What causes cat cancer?

Just as in human medicine, we know some of the reasons a cat may develop cancer. However, in many cases both with man and animals, we never know the cause.

Cancer in cats can be caused by:

- Genetics

- Environmental Toxins

- Radiation

- Second hand and third hand smoke

- Excessive exposure to the sun

- Certain medications

- Viruses

....and more.

The list looks similar to the causes of cancer in people and that’s for good reason. Since animals have roughly the same anatomy, including the same organs and cell types, their cells can be just as susceptible to the harmful effects listed above.

We know, also, that some breeds of animals are genetically more susceptible to certain types of cancer just as people can be more at risk of a particular cancer if their parents or other close relatives had the disease.

What are the Symptoms of Cancer in Cats?

The symptoms can vary depending on the location of the cancer. Obviously, if it’s in the skin, you may see obvious changes in the skin in color or texture as well as possible masses, thickening, or ulceration of the skin.

One of the most well-known types of cat skin cancer is squamous cell carcinoma, most frequently found on the ears, necks and noses of white cats. This particular feline skin cancer is most often associated with excessive exposure to sunlight.

Other types of cancer may or may not have such obvious signs. Cat breast cancer, most often referred to as feline mammary cancer, can be fairly obvious except that some cats do not readily let an owner feel or look at their abdomen so it can be missed until it is very obvious.

This can be true also of feline oral cancer (cat mouth cancer). Because cats can make it almost impossible for their owners to look in their mouths, this type of cancer which could otherwise be visible is often hidden and diagnosed late in the course of the disease. The first sign may be drooling and/or a very foul smell coming from the cat’s mouth. By that time, a tumor in the mouth can be quite advanced.

Even more difficult to determine from early symptoms are malignancies of internal organs such as feline pancreatic cancer, feline liver cancer, cat kidney cancer and feline lung cancer.

Many internal cancers can have similar signs, at least in the beginning. Symptoms can include lethargy, decreased appetite, weight loss, poor hair coat, vomiting, diarrhea, and difficulty breathing.

Another complicating factor which can lead to a delay in diagnosis and treatment is the way that cats mask how they feel. They often show no signs until their disease is in an advanced stage.

Diagnosis of Feline Cancer

A diagnosis of cancer begins with a good history from the owner, a thorough physical exam and possibly blood work, urinalysis, and a fecal exam. A diagnosis of cancer in cats can be difficult to make if the cancer is of the type that is not visible to the naked eye.

A tumor in the abdomen that is large enough to be felt during the physical exam is the exception. The abdomens of most cats, due to their small size, can be easily assessed to determine if the size of the organs is normal and if there is anything felt in the abdomen that should not be there.

However, by the time a veterinarian can feel a tumor in the abdomen, it may be later in the disease process and carry a less than desirable prognosis. In addition, there are cancers of the various organs that do not consist of one easily felt mass, but instead may be diffuse (spread out more thinly over a large area - not concentrated in one discrete tumor).

If a lump is in the skin or other area easily seen by the naked eye (mouth, ears, eyes, etc.), then your vet may have a feeling, based on education and experience, as to whether or not it is likely to be malignant (cancer). However, there can NEVER be a definitive diagnosis of cancer of any type without a sample of tissue being submitted to a pathologist for specialized testing. That is why a biopsy will be recommended. Without it, your veterinarian cannot tell you positively if your kitty has cancer or not.

A suspicious of cancer is sometimes raised when a cat is continuing to show signs of illness such as vomiting, diarrhea, weight loss, lack of appetite, or lethargy and there are no abnormalities in the physical exam or blood work to suggest another disease. Your veterinarian will then probably recommend further testing in the way of x-rays, ultrasound, or other advanced imaging studies (MRI, CT scan, etc.)

In summary, a suspicion of cancer in cats can be based on the history, physical exam, blood work, urinalysis and fecal exams; additional evidence may be obtained from x-rays and ultrasound or even MRI and CT Scans. However, a biopsy, a tissue sample, is always necessary to definitively diagnose cancer.

Cat Cancer Treatment

Just as cats have the same anatomy we do and can get the same types of cancers we do, the treatment of cancer in cats is almost identical to the treatment of cancer in people.

Surgery may be considered if the cancer is in a location where it can be removed and is one mass or a limited number of masses that can be safely removed. If the mass cannot be completely removed, your veterinarian may still recommend surgery to remove the portion that can be and then follow-up chemotherapy and/or radiation may be used.

There are some types of cancer that are not amenable to surgery and do best with just chemotherapy and/or radiation. An example of this would be lymphosarcoma (also called lymphoma) of the GI tract. This is one of the most successfully treatable cancers in cats and responds best to just chemotherapy, unless there is a mass large enough to obstruct the intestines that requires removal first.

Should I Put My Cat Through Cancer Treatment?

The clients in my practice over the last 20 years that have had the misfortune of having their cat diagnosed with cancer generally fall into 1 of 2 groups when it comes to the treatment of cancer in cats. Some clients want to do everything possible, even if the prognosis is poor. The other group does not want their kitties to undergo chemotherapy or radiation at all.

It is a personal choice, a decision that must be made by you and your family members. Your veterinarian can give you information about the options, but ultimately it is your decision.

I have seen cats cured completely of cancer as the result of surgery or chemotherapy or a combination. I have seen others who became even more debilitated by the cancer treatment and were not cured. I have also experienced the treatment of cancer in cats that didn’t make them ill, but did not end up extending their lives at all. Unfortunately, one never knows for sure which way any particular case is going to turn out.

Prevention and Early Detection of Cancer in Cats

Just as human tumors are staged according to aggressiveness and degree of development (early, late, etc.), so are the tumors found in cats. It shouldn't be a surprise to learn that the earlier cancer is diagnosed in a cat, the better the chances of treatment and a better prognosis.

As veterinary medicine has advanced over the years, your cat's yearly exam (or more often than yearly in older cats) has become more and more about the physical exam and less about just vaccines. Your veterinarian can find early warning signs of cancer in cats from a good history and physical exam, long before you would notice anything at home from your cat's behavior.

For this reason, I strongly recommend regular check-ups for your cat even if you feel your kitty is perfectly healthy. By the time a cat acts sick, it is often too late, especially where cancer is concerned.

I often receive questions related to cat cancer from readers all around the world. Here is one from Barry in Germany about mammary cancer in cats.


I have a female calico, 9 years old. She has one enlarged teat. She does not appear to be in any pain. She has never had kittens and is a totally indoor cat.


Dear Barry,

Anytime cat teats are enlarged, there is cause for concern. Cat mammary tumors are pretty much always the cause and they are almost always malignant.

If cat mammary tumors are detected early and removed surgically, there is a good chance for complete recovery.

Cat teats should always be uniform in size and the fact that it's only one that is enlarged makes it more likely that it is a tumor.

Cat mammary tumors, if not removed, spread to the adjacent teats and become very enlarged and tend to ulcerate. They also metastacize to the lungs and lead to death.

I strongly recommend you take her to the vet right away for a complete exam, including an exam of the enlarged teat. Most likely, the vet will want to do a biopsy or completely removal and will want bloodwork and x-rays of the lungs first.

Again, enlarged cat teats are almost always malignant cat mammary tumors and need vet attention right away.

Thank you for writing and I hope things work out ok.
Dr. Neely

As you scroll further down this page, you will find many other questions and answers about cat cancer to read.

Go From Cancer in Cats
To A Very Informative Page About Mammary Cancer

Read About Difficult Decisions in Feline Cancer

Return from Cancer in Cats to our HOME Page, The Cat


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