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Canine Cancer

Coping With Cancer

  • Cancer is extremely common in pets.
  • Cancer can be successfully managed in many cases.
  • Most pets tolerate treatment extremely well.
  • An accurate diagnosis and proper staging of a pet’s cancer are essential in order to pursue the best treatment and achieve the best possible outcome.
  • Cancer treatment in pets is designed to provide the best quality of life for the pet for as long as possible.
  • Monitor your pet closely throughout treatment.
  • Discuss euthanasia options with your veterinarian and outline a plan so you know how to proceed if necessary.

What You Need to Know

Cancer is extremely common in pets. While a diagnosis of cancer in a beloved pet can be devastating, it is important for owners to realize that many forms of cancer can be successfully treated or managed to provide the pet with an excellent quality of life. It is also important to realize that in pets, just as in people, some types of cancer are now viewed as a chronic, rather than terminal, disease. The best way to fight cancer is to detect it early and begin treatment promptly.

Signs of Cancer

To detect cancer at its earliest, be sure to bring your pet in for regular veterinary examinations. Between examinations, monitor your pet for signs of cancer and schedule a checkup if any of the following appear:

  • Abnormal lumps, bumps, or swellings anywhere on the body
  • Sores or lesions that do not heal
  • Unexplained weight loss or changes in appetite
  • Bleeding or discharge from any body opening
  • Unpleasant odor
  • Difficulty urinating or defecating
  • Persistent lameness
  • Drooling or any signs of mouth discomfort

Diagnosing Cancer

If cancer is suspected, it is very important for you and your veterinarian to have as much information as possible when making serious decisions regarding treatment. An accurate diagnosis is essential. Your veterinarian will also want to correctly stage your pet’s cancer. This will help your veterinarian determine how advanced the cancer is and what the projected success rates of various possible treatments might be. As a result, your veterinarian may recommend diagnostic procedures such as laboratory tests, biopsies, X-rays, ultrasound studies, and even exploratory surgery.

Treating Cancer

The goal of cancer treatment in pets is to provide the pet with the highest quality of life for as long as possible. Cancer treatments such as chemotherapy and radiation are generally tolerated extremely well by canine and feline patients.


When side effects occur, your veterinarian can prescribe anti-nausea and pain medications, as needed, as well as nutritional support to keep your pet comfortable during treatment.

In some cases, the cancer may be so advanced that your veterinarian may recommend palliative care only. This means that your pet’s veterinary team will seek to keep your pet as comfortable as possible for as long as possible without pursuing more aggressive treatment options. The primary goal of cancer care in pets is always to maintain the best quality of life possible for your pet.

What You Can Do to Help Your Pet Cope

Be your pet’s advocate. Watch your pet closely for signs that he or she is either doing well or experiencing pain or discomfort, and keep your veterinarian informed.

Keep all scheduled veterinary appointments and stay in contact with your veterinary team. It is there to help you.


Provide your pet with lots of comfort care. Spend as much time as possible with your pet; provide a quiet, comfortable place to rest and sleep; and provide nutritional support and plenty of fresh water as needed. Your pet may need to urinate and defecate more often because of cancer treatment, so make your pet’s “bathroom” as accessible as possible.

Above all, enjoy your time with your pet!

Euthanasia Considerations

In the course of your pet’s cancer care, you may realize that the “bad” days are starting to outnumber the “good” days. When you feel that you have done the best that you, in your personal circumstances, can do for your pet, you may need to consider euthanasia. Many resources are available through your veterinarian or online to help you with this difficult decision. Most owners weigh not wishing to see a pet suffer against the desire not to deprive a pet of any remaining “good” days. When this time approaches for you and your pet, be sure to keep the lines of communication open with your veterinarian. Consult with him or her closely about your pet’s medical status and learn what to expect in the days or weeks ahead. Make sure you know what the practice’s procedures are for an emergency euthanasia, both during the business day and after hours, if your pet takes a sudden turn for the worse. Monitor your pet closely for signs that he or she may be in discomfort, and discuss these signs with your veterinary team.

Many owners worry about putting their pet through cancer treatment. However, pets typically handle cancer treatment extremely well.

 

Lymphoma (Lymphosarcoma)

  • Lymphoma, or lymphosarcoma, is a cancer of the lymphocytes, which are a type of white blood cell associated with the immune system.
  • The exact cause of lymphoma is unknown.
  • Cats that are positive for feline leukemia virus (FeLV) are more likely to develop lymphoma than cats that test negative for the virus.
  • Boxers, Golden Retrievers, and Basset Hounds are at higher risk for the disease.
  • Signs vary, depending on the part of the body affected, and may include enlarged lymph nodes, loss of appetite, weight loss, lethargy, coughing, difficulty breathing, vomiting, and diarrhea.
  • Diagnosis usually requires a sample of the affected tissue.
  • Treatment is usually not curative, but it may cause the cancer to temporarily go into remission.
  • Chemotherapy is usually the treatment of choice for lymphoma.

What Is Lymphoma?

Lymphocytes are white blood cells that normally work to protect the body as part of the immune system. Occasionally, a change occurs within the cells that causes them to become destructive and reproduce uncontrollably. This is a type of malignancy, or cancer, called lymphoma or lymphosarcoma.

Dogs and cats may be diagnosed with lymphoma. Boxers, Golden Retrievers, and Basset Hounds are dog breeds that are at a higher risk for developing this type of cancer.

What Causes Lymphoma?

The exact cause of lymphoma is not known. However, cats that are positive for the feline leukemia virus (FeLV) are much more likely to develop lymphoma than cats that test negative for FeLV.

What Are the Signs of Lymphoma?

The signs of lymphoma can vary, depending on the part of the body affected. With generalized lymphoma, the pet may have enlarged lymph nodes, which can appear as swellings in the neck at back of the jaw, behind the knees, and other locations. The pet may seem relatively healthy or experience lethargy (tiredness), loss of appetite, and weight loss.

Mediastinal lymphoma occurs inside the chest. Pets with this kind of lymphoma may experience coughing and difficulty breathing. When lymphoma is in the gastrointestinal tract, cats and dogs may show signs of vomiting, diarrhea, and blood in the stool.


Lymphoma can also affect the spinal cord, kidneys, eyes, nose, and skin. Signs are associated with the affected organ, such as impaired movement with spinal lymphoma, increased drinking and urinating with kidney lymphoma, and raised growths on the skin with skin lymphoma.

How Is Lymphoma Diagnosed?

Your veterinarian will most likely recommend blood work, including an FeLV test for cats. Radiographs (x-rays) of the abdomen and/or chest can also be important to help identify affected regions of the body. An ultrasound exam of the chest or abdomen may help your veterinarian identify tissue abnormalities and affected lymph nodes.

A biopsy sample from the affected tissue is the best way to diagnose lymphoma. In some cases, lymphoma in dogs can be diagnosed from a lymph node aspirate sample, which involves placing a needle in the lymph node and extracting cells for examination under the microscope. However, a biopsy is the best way to determine the exact type of cell involved, as well as the aggressiveness of the tumor, if treatment will be pursued.

How Is Lymphoma Treated?

In many cases, treatment of lymphoma can cause the disease to go into remission, meaning that the signs of cancer resolve. This is usually temporary, and the lymphoma eventually returns.

If you wish to pursue treatment, your veterinarian may refer you to a veterinary oncologist, who specializes in cancer treatment. Additional tests may be needed to stage the disease or to determine how much of the body is involved.

In cases where the lymphoma is limited to one location, such as the nose, radiation therapy may be an option, but most treatment involves chemotherapy. Animals typically tolerate chemotherapy better than humans, but treatment may require several office visits and additional blood tests, which can become expensive.

If you choose not to pursue chemotherapy, treatment with steroids may help reduce the signs of lymphoma and make your pet more comfortable for a time.

Can Lymphoma Be Prevented?

There is no known way to prevent lymphoma, but early diagnosis and intervention can improve quality of life for pets with the disease. Early testing for FeLV can identify cats at greater risk for developing lymphoma. Cats that test positive for FeLV should be kept indoors to minimize exposure to other cats.

Cats that test negative for FeLV are less likely to develop lymphoma. If your cat is negative for FeLV and must go outdoors, make sure he or she is vaccinated against FeLV. Keeping your cat indoors can help prevent exposure to FeLV-positive cats and reduce the need for FeLV vaccination.

Breast Cancer in Dogs and Cats

  • Breast cancer is the uncontrolled growth of abnormal mammary gland (breast) cells.
  • Tumors occur most frequently in older female pets who have not been spayed.
  • Most (80 to 90 percent) mammary tumors in cats are malignant (cancerous), while 50 percent of mammary masses in dogs are malignant.
  • While the cause of breast cancer is unknown, hormones are thought to play a role.
  • Signs of breast cancer include firm nodules in the tissue around the nipples, ulcerated skin, and swollen, inflamed nipples with or without discharge.
  • Breast cancer is best diagnosed with a surgical biopsy.
  • Blood work and radiographs (X-rays) are usually recommended to help determine if the cancerous cells have spread to other parts of the body.
  • Tumors are treated with surgical removal and possibly radiation therapy and/or chemotherapy.
  • Spaying female pets before their first heat cycle is the best way to prevent breast cancer.

What Is Breast Cancer?

Breast cancer is the uncontrolled growth of abnormal mammary gland (breast) cells. If left untreated, certain types of breast cancer can metastasize (spread) to other mammary glands, lymph nodes, the lungs, and other organs throughout the body.

While any pet can develop mammary tumors, these masses occur most often in older female dogs and cats that have not been spayed. Siamese cats have a higher risk for breast cancer than other feline breeds.


In cats, 80 to 90 percent of these tumors are malignant (cancerous). Dogs fare a little better: Fifty percent of mammary tumors are malignant. Any suspicious lump in the mammary area should be examined by a veterinarian as soon as possible.

What Causes Breast Cancer?

The exact cause of mammary gland cancer is unknown. However, dogs and cats that are spayed before their first heat cycle are less likely to have breast cancer, so hormones may play a role.

Treatment with hormones for other conditions may increase the risk for this type of cancer. In the past, hormones were used to treat some behavior and skin problems in cats, but this has generally fallen out of favor. Some hormone treatments are still being used in dogs, such as estrogen in the treatment of urinary incontinence, but other alternatives are usually available.


Genetics may also play a factor in canine breast cancer. Recent findings show that certain genes are overexpressed in dogs with this condition.

What Are the Signs of Breast Cancer?

There’s no way to determine if a lump is cancerous simply by feeling it. But since any lump in the mammary area has the potential to be cancerous, it’s a good idea to check your pet regularly.

Mammary tumors tend to be firm, nodular masses that feel like BB pellets under the skin. Tumors may be located in a single mammary gland (the area around one nipple), or they may be in several mammary glands at once. The skin covering the tumor may be ulcerated or infected. Nipples may be swollen or red, and there may be discharge from the nipple itself.

How Is Breast Cancer Diagnosed?

The best way to diagnose breast cancer is with a surgical biopsy (tissue sample) of the mass. In dogs with large masses, it may be possible to obtain a fine needle aspirate of the tumor, which involves placing a needle into the mass and extracting cells for examination under the microscope. This procedure may be more difficult with smaller masses or in cats. Since a biopsy usually provides a larger tissue sample (likely to yield a more definitive diagnosis), this is the best option. Biopsies generally require some form of anesthesia or sedation, so your veterinarian may recommend a preanesthetic evaluation and/or blood work.

How Is Breast Cancer Treated?

Early detection and surgical removal of the masses is the best treatment option. Before performing surgery, your veterinarian will most likely recommend blood work and radiographs (X-rays). Chest radiographs are important to check for metastases to the lungs, and abdominal radiographs may show signs of enlarged lymph nodes. If the radiographs show no evidence of metastasis, the pet has a better prognosis.

Because of the high rate of malignancy in cats and the fact that cancer often invades several mammary glands along the same side of the body, a radical mastectomy with removal of all mammary glands on the same side is often recommended. For cats with masses on both sides, two separate surgeries several weeks apart may need to be performed.

Unless dogs have multiple tumors, they may not need to have as much tissue removed as cats. Submission of the tissue for microscopic examination will determine if the tumors have been completely removed.

If your pet still has her ovaries and uterus, your veterinarian may recommend spaying your pet at the time of mammary surgery.

Following surgery, your veterinarian may recommend radiation therapy or chemotherapy. Radiation therapy is designed to kill any potentially cancerous cells in a focused area. Chemotherapy involves systemic drugs that treat cancerous cells that may have traveled to other parts of the body.

Can Breast Cancer Be Prevented?

The best way to prevent breast cancer is to have your pet spayed before her first heat cycle. Even spaying your pet by 1 year of age can help reduce breast cancer risk. Pets that are spayed later in life will be at higher risk for breast cancer.