The 5 Most Common Cancers in Dogs and Cats

Cancer is a scary and common fatal disease among humans, cats, and dogs. Learn what the most common cancer is and how you can prevent your pets from getting sick.

The 5 Most Common Cancer Types in Dogs and Cats

Like people, dogs and cats fall ill. Certain diseases like cancer are a common diagnosis among man’s furry friends, especially among dogs. In fact, one-fourth of all dogs are diagnosed with cancer and nearly half of all elderly dogs die from cancer or cancer-related causes.


Pets, like humans, get cancer when abnormal cells in the body divide and multiply, usually materializing as tumors before they spread to the blood or tissue of your cat or dog. Finding out your pet has cancer can be a scary experience, but not uncommon today.

In fact, one in every three dogs will receive a cancer diagnosis at some point in their lifetime, and half of all dogs over the age of 10 will develop cancer according to the AVMA. But the good news is that around half of all canine cancers, and many feline cancers as well, as treatable when they are found early.

Cancer can come in many forms and occur in any breed, whether mixed breed or purebred. Learn what some of the most common cancers found in dogs and cats are as well as what symptoms, treatments, and prevention methods may be available to help keep your pets healthy and happy.


The most common type of cancer in both cats and dogs, lymphoma occurs twoto five times as frequently in canines than in humans.

a dog not feeling well

In cats, feline immunodeficiency virus or feline leukemia virus severely increases the chance of a lymphoma diagnosis. Cats with leukemia virus often get lymphoma in their kidneys or intestinaltract. But in many cases (in dogs or cats), lymphoma begins with swollen glands you can feel or see in the following areas:

  1. Under the neck
  2. Behind the knee
  3. In front of the shoulders

Sometimes this disease comes with chest or abdominal lymph nodes that cause breathing or digestive issues, and if the cancer is especially aggressive, it can be unresponsive to treatments.

Dogs can be affected at any age, and some breeds may have a higher likelihood of getting lymphoma than others. They are often treated for lymphoma based on the stage of the illness when the diagnosis is made, and the cause is unknown. A vet may choose to complete the following to find the stage of cancer:

  1. Abdominal ultrasound
  2. Radiographs
  3. Biopsies
  4. Chemotherapy

Mammary Tumors

Also known as breast cancer, the first signs of mammary tumors in pets are often overlooked. The tumors can be small in size and they present themselves around the animal’s nipple. It is malignant in half of all cases, and most have spread by the time surgery is attempted to remove the tumor. However, this type of cancer can be painful.

dog not feeling well

Mammary Tumors are commonly found in female cats that are at least 6 years of age or older. Your cat has a drastically less chance of getting this type of cancer if she is spayed at a young age, especially before she goes into heat for the first time.

Although more common in cats, female dogs are commonly affected as well. According to the American College of Veterinary Surgeons, mammary tumors often pop up in female dogs that were not spayed or spayed after two years of age.

Skin Cancer

Changes in the skin or lumps can be a typical sign of skin cancer, and although not all are cancerous, surgical removal can be required as treatment. There are a few different types of skin cancer often found in pets, including adenocarcinoma, melanoma, and squamous.

dog having skin cancer

Squamous is one of the most common cancers found in cats that affect the skin tissue, although it has been found in all domestic animals. This cancer comes in two main forms andusually presents itself in middle-aged animals. The first sign will often be a scratch on a cat’s nose or dog’s belly (somewhere that doesn’t get much sunlight) or a red wound or mound near the mouth that doesn’t seem to heal.

Treatments vary, but early freezing treatments or more aggressive radiation treatments combined with surgery commonly cure this disease. If combined with a head or neck cancer, however, you may need to consider more serious treatments.

Melanoma, on the other hand, is very common in both types of pets. It can be found in the footpads, nail beds, or eyes. However, the first signs may appear around the lips or mouth, or appear like a swollen paw, mouth sore, or eye that constantly drains. These tumors are aggressive and typically take over vital organs quickly.

Mast Cell Cancer

This type of cancer often presents itself with tumors on the liver, spleen, or skin. Often found on the skin, mast cell tumors can affect other tissues like the respiratory tract or the intestines. These mast cells contain histamines and enzymes that function as protecting the body until the tumors form. Then, protection turns against the immune system entirely.

mast cell cancer

The first sign is often a lesion on the skin, and some mast cell tumors are uncomfortable. As a result, many pets act or feel agitated. It’s most common in dogs but can also affect felines. Ineither pet, detection can be tricky because they can appear like a hairless raised circle or a soft lump under the skin. Sometimes they can turn into wounds or become itchy.

Older dogs and mixed breeds often fall victim to mast cell cancer, although some breeds are particularly affected more than others, including the following:

  1. Boston Terriers
  2. Labrador retrievers
  3. Boxers
  4. Beagles
  5. Schnauzers

Diagnosis for this type of cancer often includes a hypodermic needle, which is used to suck out the cancer cells and studied as a slide. Mast cell tumors are often curable, and the testing is easy to perform without sedation.

Bone Cancer

The tumors for this type of cancer can grow very quickly, however, 85 percent of osteosarcoma tumors are malignant. Osteosarcoma is still a very a serious and common form of cancer in both dogs and cats. A type of bone cancer, osteosarcoma usually affects the hind legs and shoulders of felines or larger breeds of dogs; although, it can occur in any bone.

Try To Diagnose Problem And Act

Initial signs of this cancer are common in the limbs, and you will typically notice swelling or lameness that doesn’t seem to heal or be explainable.

Dogs between the ages of four and seven are typically affected by osteosarcoma, including the following breeds:

  1. Irish setters
  2. Rottweilers
  3. Great Danes
  4. Doberman pinschers
  5. German shepherd dogs
  6. Golden retrievers

Be Prepared

To prevent common cancers in your pets, it’s important to know your dog or cat’s potential risk for cancer. The breed of your pet and the environment you live in can play a huge role. Dogs who live on farms, for example, are exposed to a higher rate of nasal cancer due to the added amount of pesticide residue on the ground, where a dog spends a lot of time sniffing.

There are also things we can do to both help and hinder cancer risk. Some vaccines may also exist that increase your pet’s risk of cancer. On the other hand, sometimes spaying or neutering them is helpful.

How to Check Your Pet for Cancer

Now that you know about the most common cancer in dogs in cats, it’s important to check your pets every few months. It only takes around five minutes to do, and you can simply give your pets a quick check every two months or so.

a dog beside a dog food

Check your pet’s mouth and feel for any lumps under the skin, even near their butt. If you ever think you find anything, don’t hesitate to consult a vet. You may be referred to a specialist called an oncologist, who will be able to determine if cancer is suspected and make a final diagnosis.

Common possible signs of cancer may include:

  1. Refusal to eat or drink
  2. Vomiting or diarrhea
  3. Trouble breathing
  4. Lethargy

Common Treatments

The type of treatment your pet receives will depend on the type of cancer and the stage of the disease. A vet will need to determine how far the cancer has spread in the body and be able to offer more information on your pet’s chances of responding to treatment, as well as which treatment options will work better based on the type of cancer. Each type of cancer required individual care.

a dog undergoing some test

Treatments may include one therapy or a combination of a few, including:

  1. Surgery
  2. Radiation
  3. Chemotherapy
  4. Cryosurgery (freezing)
  5. Hyperthermia (heating)
  6. Immunotherapy

Like people, animals like dogs and cats respond well to chemotherapy. However, pets can tolerate the therapy better ,than most people and experience less severe side effects.

To keep your pet comfortable and happy, you may also have a pain management process. Throughout therapies, it’s important to keep an eye on your pet’s overall health. Your vet may require dietary changes or a series of therapies to help dogs or cats respond to treatment.

When the type of cancer or the stage hasprogressed beyond the point of prohibitive treatments, you may need to consider putting your pet down. Euthanasia can sometimes be cheaper than treatment options that are doomed to fail, and sometimes a pet’s quality of life is toopoor to attempt treatments.

Before you make a decision, always speak to a veterinarian. A licensed professional can help you make the best decision for you and your furry friend.

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