Pet Cancer Awareness Month

By: Cate Burnette

Veterinarians estimate the 6 million pets will be identified with various cancers this year. Cancer is the top disease-related killer of our beloved animals, with 1 in 4 dogs and cats diagnosed with a disease that accounts for 50 percent of all pet deaths. A devastating verdict for all pet parents, we need to educate ourselves on early detection, symptoms and treatments, and what we can do if our pet receives that horrible diagnosis.

Types of Pet Cancers

Just as in humans, the types of cancers, their symptoms and treatments can vary from animal to animal and species to species. The National Veterinary Cancer Registry, a national database dedicated to advancing medical treatments for these diseases, shows the connection between human and animal cancers and details some of the more common cancers for both canines and felines.

Insulinomas – An insulinoma is a malignant tumor of the pancreas usually seen in middle-aged to older medium to large-breed dogs that causes excessive secretion of insulin, the hormone produced by the pancreas that regulates blood sugar. This overproduction leads to very low blood sugar concentrations. The breeds most commonly predisposed to this type of cancers include Irish setters, Boxers, Golden retrievers, German shepherds, Poodles and Labrador retrievers. There appears to be no gender predilection. This tumor is very rare in cats.

Chondrosarcoma of the Bone in Canines – This malignant form of cancer spreads quickly, and if not diagnosed and treated early, can be fatal to the animal. Arising from the connective tissue between the bones and joints (the tendons, ligaments, and synovial tissues), chondrosarcoma metastasizes to other areas of the body, particularly the ribs and other flat bones, including the hips and the bones of the nasal cavity. This type of cancer, mainly affecting large-breed and older dogs, may also affect the limbs, resulting in weakening bone structures that can lead to fractures.

Hemangioma and Hemangiosarcoma in Dogs – When hemangiomas (tumorous red-to-black nodules) and sarcomas (cancers of connective tissues, blood vessels, or the fibrous tissues around body organs) combine, they become hemangiosarcoma. Hemangiosarcoma is defined as a cancer of the blood vessels usually occurring in the heart, spleen or skin of the animal.

These tumors typically develop slowly in one or more body organs until they reach a critical, advanced stage. Because they can remain hidden, these cancers often have a poor prognosis, with the average time of discovery until death in affected animals showing as 6 to 8 weeks. Many animals will only present acute symptoms including unexplained weaknesses, pale mucous membranes, painful, abdominal swelling, and sudden collapse in the hours right before they die.

Canine Lymphosarcoma (LSA) – One of the most common tumors seen in dogs, lymphosarcoma is caused by an abnormal production of lymphocytes (those white blood cells that normally function to fight disease in the immune system). Often seen as a non-painful enlargement of the lymph nodes, this type of tumor can be felt during normal palpation by your veterinarian. As the disease progresses, the affected nodes can become so enlarged that they interfere with normal function of body organs and the flow of blood and oxygen through the circulatory and respiratory systems. Any breed or age of dog can be affected, however, Golden retrievers are considered to be most at risk for developing LSA.

Squamous Cell Carcinoma – Recognized in all domestic animals, prolonged exposure to sunlight has been determined as a major predisposing factor in this disease that arises in the skin of the animal. In felines, a distinctive form of squamous cell carcinoma is associated with the acquisition of the papilloma virus infection. Frequently found in older dogs, Bloodhounds, Basset hounds and Standard poodles are at greatest risk of developing this tumor. These firm, often ulcerated nodules are raised above normal skin level, and may appear on the head, paws, and abdominal areas.

Mast Cell Tumors – These tumors originate in the cells that are the parts of the immune system that release histamines and other substances during inflammatory and allergic reactions. The most frequently recognized malignant (or potentially malignant) tumors of canines, mast cell tumors can appear simultaneously in multiple body areas and can be seen as soft or solid raised, nodular masses. Although dogs of any age can be affected, this cancer is more common in seniors. Predisposed breeds include Boxers, Pugs, Rhodesian ridgebacks and Boston terriers.

Basal Cell Carcinomas – More frequently found in cats than in dogs, basal cell carcinomas begin in the cells that line the deepest level of the epidermis (the outermost layer of skin). The tumors can look like ulcerated sores on the head, neck or limbs of the affected animal, but rarely metastasize to other organs of the body. Senior cats of the Persian breed are predisposed to this cancer as are aging Saint Bernards, Scottish terriers and Norwegian elkhounds.

Pet Lymphoma – Lymphoma is one of the most common canine cancers and can affect any dog at any age. In most cases, lymphoma first shows as swollen glands that can be felt or seen under the jawline, behind the knee, or in front of the shoulders. Cancerous lymph nodes inside the chest or abdomen can cause breathing or digestive problems.

Pet Osteosarcoma – Osteosarcoma is a very common type of canine bone cancer; veterinarians estimate that up to 85 percent of skeletal tumors are diagnosed as osteosarcoma. More commonly found in senior giant dog breeds such as the Great Dane and the Mastiff, this type of cancer can affect dogs or any breed or size. The first signs of the disease can be swelling and pain at the site of the tumor and recurrent lameness. This tumor can be very aggressive and spreads very quickly and is often found in other body organs at the time of diagnosis.

Pet Melanoma – Melanoma is more commonly seen in dogs with dark pigmented skin and there is a known hereditary component to this tumor. However, originating as it does in the cells responsible for skin’s color, any dog may be vulnerable to this type of cancer. These tumors can be both benign and malignant; the malignant type of pet melanoma is incurable. Melanoma can form small dark lumps – or large, flat, wrinkled masses – under the hair on the skin and tend to quickly metastasize, often seen as already spread to the body’s organs upon initial examination.

This cancer appears to be uniquely responsive to immune-based therapies, leading to a vaccine now in clinical trials that works by stimulating the patient’s immune system to destroy the cancerous cells naturally, without the aid of chemotherapy or radiation.

Symptoms of Cancer in Your Pet

According to the Colorado State University Flint Animal Cancer Center, the 10 major warning signs of cancer in pets are:

  1. Unusual swellings that don’t go away – or that grow. Consistently check your cat or dog for lumps and bumps by petting and rubbing all over the body.
  2. Sores that won’t heal. A sore or injury that refuses to heal can be either a persistent infection or a sign of cancer. Your veterinarian can evaluate the issue and provide a diagnosis.
  3. Weight loss. If your dog or cat is losing weight but is not eating a calorie-restrictive diet, illness could be the reason for the pounds disappearing.
  4. Loss of appetite. A pet that is reluctant to eat or completely refuses food is another sign of some kind of possible illness and needs to be seen by your vet.
  5. Bleeding or discharge. Abnormal bleeding, unexplained vomiting and consistent diarrhea can all signal a problem that needs diagnosis and treatment.
  6. Offensive smell. An unpleasant odor coming from your pet’s anus, mouth or nose is a common sign of tumors.
  7. Difficulty eating or swallowing. A common sign of cancers of the mouth or neck, this sign exhibits with excessive drooling, choking, coughing or dropping of food while eating.
  8. Reluctance to exercise or low energy level. Lethargy or exercise resistance is often one of the first signs that your pet is not feeling well.
  9. Persistent lameness. There can be many causes of lameness (limping, reluctance to either lie down or rise, inability to negotiate stairs) including nerve, muscle, or bone cancers.
  10. Difficulty breathing, urinating, or defecating. Any of these symptoms exhibited by your pet should be considered a veterinary emergency and requires an evaluation by your veterinarian as soon as possible.

Veterinary Diagnosis

If a lump is present, the first step is typically a needle biopsy, which removes a very small tissue sample. This sample can be sent to a lab for examination and diagnosis. Alternatively, the pathologist may want to examine all or part of the lump that needs to be removed through surgical excision. Radiographs, ultrasound, blood evaluation and other diagnostic tests may also be helpful in determining if cancer is present or if it has spread.

Veterinary Cancer Treatments

Treatment options vary and depend on the type and stage of cancer. Common veterinary managements include surgery, chemotherapy, radiation and immunotherapy. A combination of therapies may be used and you may need to take your affected pet to a specialist for treatment. Success of cancer therapy depends on the form and extent of the cancer and the aggressiveness of the treatment. Of course, early detection is best.

Some holistic veterinarians may recommend a more natural approach to cancer therapy that includes supplementing with digestive enzymes, Omega-3 fatty acids, antioxidants, medicinal mushrooms and herbs, and homeopathy. Acupuncture, massage therapy, electromagnetic radiation, and an organic, whole foods diet may also be suggested.

It is up to you, as a loving pet parent, to do your research and determine the best form or treatment for your pet.

Some pet owners opt for no treatment of the cancer at all, in which case palliative care, including pain relief, should be offered. Regardless of how you proceed after a diagnosis of cancer in your pet, it is very important to consider the quality of life when making future decisions.

Prognosis of Cancer in Pets

Some tumors are very aggressive, and treatment for these may be unrewarding. But others can be cured. Most are treated as chronic diseases in veterinary medicine. This means that a patient may eventually go on to succumb to the disease, but treatment is targeted to give the patient a good-to-great quality of life for a substantially longer time period than would otherwise be possible. For many pet owners, this benefit is well worth it. Certainly, it pays to seek advice and second opinions as early as possible in the course of the disease and to learn what is possible for your pet and the particular cancer diagnosed.


Cate Burnette is a semi-retired registered veterinary technician with clinical experience in small and large animal medicine. With 30-plus years of journalism experience, she went back to school after 9/11 to work with her first love: animals. The pet parent of four cats, three dogs and one ex-racehorse, Cate is a certified rescue volunteer with the American Humane Association’s Red Star Emergency Services and served with the group in New Orleans doing animal search and rescue after Hurricane Katrina. She is also a horse safety and horse management expert, and has volunteered with US Pony Clubs as a district commissioner and horse management judge.