Pet Cancer - things to know

pet cancer benign and malignant images

What is Cancer

Cancer is a disease in which some of the body’s cells or tissues grow uncontrollably and spread to other parts of the body. Thankfully, not all abnormal growths are cancerous. Some are benign. They tend to not invade surrounding tissues and progress slowly. Malignant growth can be unpredictable in terms of the rate of growth and invasion of surrounding tissues. Only malignant growth of cells is referred to as cancer.

Symptoms of Pet Cancer

If your pet exhibits any of the following cancer symptoms, it could be a red flag for their health. There are many types of cancer, and different breeds of pets may have unique symptoms. Keep in mind that these symptoms are not exclusive to cancer, so there’s no need for excessive fear or worry. Monitor your pet and see your veterinarian. Many symptoms can be for treatable conditions.

Common pet cancer symptoms:
  • Unusual lumps or bumps under your pet’s skin
  • Unexpected and lasting weight loss or weight gain
  • Your pet suddenly acting very tired and listless 
  • A bad smell from your pet’s mouth or other body part
  • Big change in appetite

In addition to the common symptoms, we have also compiled a list of prevalent cancers, categorized by pet type (dogs and cats). Click to view the relevant information as needed.

cat being examined by vets

Common Cancers in Cats

Lymphoma is a type of cancer that affects immune cells called lymphocytes. Since these cells travel all around the body in both blood and lymphatic vessels, lymphoma is considered a widespread disease, not just a local issue. It’s quite common in cats, making up around 30% of newly diagnosed feline cancers.


  • Weight loss
  • Vomiting
  • Diarrhea
  • respiratory difficulties
  • Lymphoma does not cause acute pain
  • some cats have a decreased appetite, some have an increased appetite, while others have no change in appetite.

Feline soft tissue sarcomas are malignant tumors. Most commonly, these tumors are found over the chest, back, side, legs and facial tissues of pets. Most of the time, these tumors grow slowly. However, in some cases, they can be aggressive and spread rapidly. About 7% of all skin cancers in cats are soft tissue sarcomas.


  • you can feel a lump or mass under skin
  • Lameness
  • Vomiting

 Squamous cell carcinoma (SCC) is a type of skin cancer that is usually harmless and easy to treat if caught early. However, if left unnoticed, it can get worse, spread to other parts of the body, and even become deadly. They can occur in various areas, but they most commonly show up in the mouth. The cancer is usually detected by a doctor handling and petting during a cat’s examination.


  • Trouble with eating
  • Bad Breath
  • Weight loss
  • Drooling or salivating excessively
  • Swollen upper or lower jaw

This is another form of cancer in cats, but fortunately, mammary cancer is one that can often be prevented by spaying. Cats spayed before six months are seven times less likely to develop this cancer than cats spayed after six months. 

Cornell University’s College of Veterinary Medicine found that about 85% of these cat breast cancers are deadly malignant adenocarcinomas. These harmful growths start in the gland tissue under a nipple and can eventually spread to other parts of the body.

This type of cancer happens mostly in female cats (over 95% of the time) and is most common in cats older than 10 years. If your cat is older in age, this might be one of the diseases you need to pay attention to and take preventive measures for.


  • One or more palpable masses underneath the skin in the stomach area
  • Skin over the lump may open and bleed, feel warm, or become painful
  • Your pet may excessively groom the area, causing a strong odor due to infection

If cancer has spread,

  • eats less, is lethargic,  loses weight
  • sometimes breathing problems or persistent coughing

Common Cancers in Dogs

Lymphoma is a cancer of a type of blood cell (lymphocytes) and lymphoid tissues.  Lymphoid tissue is normally present in many places in the body, including lymph nodes, spleen, liver, gastrointestinal tract and bone marrow.


  • Firm, enlarged, non-painful lymph nodes
  • Decreased appetite
  • Lethargy
  • Weight loss
  • welling of the face or legs 
  • occasionally increased thirst and urination

Mast cell tumors are a type of skin cancer. Mast cells are found in connective tissues, especially near the outer surfaces of your dog’s body, like the skin, lungs, nose, and mouth. These tumors are graded based on their location in the skin, inflammation levels, and how distinct they are. Some small lumps can be hard to detect with just your eyes or by touch.


  • A new skin mass 
  • Vomiting
  • Diarrhea
  • Peripheral edema 
  • Fever and collapse

Melanoma is a common type of cancer in dogs and is the most common malignant tumor of a dog’s mouth.   Skin tumors are among the most common tumors found in dogs and many are benign.


  • Poor appetite and weight loss 
  • Bad breath and abnormal chewing behavior
  • Tooth loss
  • Bleeding from the mouth

Osteosarcoma refers to the most common bone tumor found in dogs. Bone cancer can affect any breed of dog, but it is more commonly found in the larger breeds.

If left untreated, osteosarcoma can quickly spread throughout the body and may lead to a range of other health issues, potentially becoming fatal rapidly. However, if osteosarcoma is diagnosed early, there is a high chance it can be cured.


  • Swelling in the ribs, spine, legs, or jaw
  • Severe pain
  • Mass or lump on the dog’s body
  • Loss of appetite
  • Limping or lameness
  • Respiratory distress
  • Discharge from the nostrils
  • Lethargy or weakness

Hemangiosarcoma is a highly malignant cancer that can spread rapidly, causing tumors almost anywhere in the body, and is a disease of larger-breed, older dogs. It is most often found in the dog’s heart and spleen (rich blood supply sites). Many times it is in the advanced stage before it is diagnosed.

In addition, unfortunately, no clinical signs are classic for hemangiosarcoma other than sudden, profound, internal bleeding.

What do I do if I suspect Pet Cancer?

Make an appointment with your vet!

If you think your pet has these symptoms don’t delay. Book an appointment with your vet to check it out.

To diagnose your pet’s disease, appointments could include blood work, urinalysis, biopsy, fetal test, or other tests, depending on your pet’s symptoms.

Costs of Treating Pet Cancer

The treatment and costs will vary depending on the cancer diagnosed by your veterinarian.

According to the Vet Cancer Society, the average cost for  treatments can be somewhat like this:


Cost ($)

Initial visit / diagnostics


Major surgery to remove a cancerous tumor


Chemotherapy dose 


Chemotherapy full treatment series 3,000~5,000
Radiation therapy 2000~6000

How to Find Help

Always start with what is in the best interest of the pet and its quality of life.

If treatment is advised by your veterinarian and your pet is young and otherwise healthy, you may have to look for financial aid. Treating cancer is very expensive!  

Discuss payment options with your veterinarian. There may be options such as:

  • Credit care: helps you pay out of pocket for healthcare expenses including pets 

Another alternative if you qualify as low-income is to look for non profit assistance.  Check this list of non-profit organizations 

Pet insurance may cover treatment costs, but only when your pet is enrolled in the insurance program before diagnosing the cancer. If your pet already has cancer, you won’t find a policy to cover pre-existing conditions. If you buy a breed known to commonly develop cancer, it may be worth considering pet insurance.

Sadly not all cancers can be treated

It is excruciating to watch your adorable pets suffer. Be prepared to do the right thing. 

Compassionate euthanasia is an option if your pet’s quality of life is seriously affected by the disease. Euthanasia is the act of putting your beloved pets forever to sleep with an injectable drug.

If you’re unsure whether it’s time or not, have a quality-of-life consultation with your veterinarian. They will consider all the factors to help you make the right decision. 

Read More – How to know when it is time for euthanasia