Cancer in Dogs and Cats The Causes, Symptoms, and Treatment Options for Pets with Cancer

Cancer in Dogs and Cats
expert or vet photo
vet verified PetCareRx Staff Veterinarian DVM

Thumbnail of Piroxicam


Arthritis & Pain
{{petcare_price|currency}} Price in Cart w/PetPlus {{petplus_price|currency}} See PetPlus Price in Cart

Cancer is an all too common diagnosis for cats, and even more so for dogs. Learn about the types, causes, and various treatments for cancer in pets.

Cancer is an all too common diagnosis for cats, and even more so for dogs. Approximately one-fourth of all dogs will be diagnosed with cancer in their lifetime. Older dogs have an even higher likelihood of a cancer diagnosis; half of all older dogs will pass away from cancer. Cats are not free from the diagnosis either; feline friends are also heavily at risk for cancer. Cancer in pets, just like cancer in humans, occurs when abnormal cells divide and multiply. It can materialize as tumors, or be spread in the blood or tissue of a cat or dog.

5 Most Common Cancers in Cats

Some of the most common types of cancer that cats can get are:

1. Lymphoma

Having feline immunodeficiency virus (FIV) or feline leukemia virus (FeLV) drastically increases the likelihood of your pet being diagnosed with lymphoma. Most cats with FeLV are struck with lymphoma that could be in the intestinal tract or kidneys.

2. Mammary Tumors

A common cancer for older female cats that are over 6 years of age, mammary tumors, or breast cancer, can be drastically reduced if a cat is spayed early in life, particularly before she first goes into heat.

3. Skin Cancer

Not all skin changes or lumps are a sign of skin cancer, but many can be  cancerous, either malignant or benign. Generally surgical removal is the main form of treatment. Squamous cell carcinoma is one particularly prevalent form of skin cancer in cats, and often develops in the mouth. Adenocarcinoma and melanoma are other forms of skin cancer.

4. Mast Cell Cancer

Mast cell tumors can appear on the skin or within the spleen or liver.

5. Osteosarcoma

A form of bone cancer, osteosarcoma occurs in the legs (often the hind legs) and shoulders of cats.

4 Most Common Cancers in Dogs

Some of the more common cancers to afflict dogs are:

1. Lymphoma

The cause of lymphoma in dogs is unknown, and the stage of the illness has a sizable impact upon the prognosis. Biopsies, abdominal ultrasounds, and radiographs are performed to find the stage of the lymphoma.

2. Bone Cancer

Osteosarcoma is a common form of bone cancer in dogs, particularly in larger breeds.

3. Mammary Tumors

As in cats, mammary tumors are more common in unspayed females. Not all the tumors are cancerous, but surgery is generally recommended even for non-malignant tumors.

4. Hemangiosarcoma

This is a common cancer in dogs and generally occurs in mid-range to older aged dogs. The tumors are usually found in the liver or the spleen.


One of the most important symptoms of cancer to watch for is lumps and bumps on your pet’s skin or just below. Also important to look for are any behavioral changes in your cat or dog. A loss of appetite and corresponding loss of weight should always be a concern, and are frequently an indicator of cancer. Vomiting, diarrhea, and unusually colored feces can also be symptoms of cancer. Changes in your pet’s attitude, from a reluctance to exercise or play to an alteration in disposition can also reveal a major health problem.


The treatment for cancer in pets can take the form of surgery, chemotherapy (cancer drugs for dogs and cats), or radiation depending on the form of cancer that your pet has, as well as its stage and severity. In many cases, the goal of treatment is mainly targeted at easing your pet’s symptoms. Unfortunately, treatment of cancer in pets is often not possible, or will only extend a pet’s life by mere months.


Some forms of pet cancer can be prevented with the use of vaccinations and by spaying or neutering the cat or dog. Be sure to ask your vet about the history of the vaccine's use--a vaccine that used to be used for FeLV was linked to a type of cancer called fibrosarcoma. The vaccine's makeup has since been changed, but it's always a good idea to ask your veterinarian how long a vaccine has been in use and what possible side effects there may be.

As with cancer in people, both genetics and environmental factors can play a role in determining which pets get cancer, and which avoid it. While it is difficult to pin down the precise causes of cancer, and there is no foolproof prevention method, helping your pets avoid exposure to chemicals and the sun is a smart prevention strategy. Certainly, though, as with humans, there is no foolproof way to ward off a cancer diagnosis and much is unknown about why pets contract the disease.

More on Cancer in Pets

All About Histiocytosis in Pets

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

Was this article helpful?
Bone Cancer Mast Cell Tumors Cancer

You May Also Like

Image for Ways To Treat Hemangiosarcoma In Cats
Ways To Treat Hemangiosarcoma In Cats

An Aggressive Cancer of the Blood Cells

Read More
Image for Meningioma In Dogs And Cats
Meningioma In Dogs And Cats

The Most Common Brain Tumor

Read More
Image for Lymphoma in Dogs and Cats
Lymphoma in Dogs and Cats

Cancer in Pets - Lymphosarcoma

Read More