Cancer in animals

- From the American Veterinary Medical Association

What is Cancer?

Cancer is an uncontrolled growth of abnormal cells on or within the body. Cancer may be benign or malignant. It may be localized or it may invade adjacent tissue and spread throughout the body.

How Common is Cancer?

Cancer is common in pet animals and the incidence increases with age. Cancer accounts for almost half of the deaths of pets over 10 years of age. Dogs get cancer at roughly the same rate as humans, while cats get fewer cancers.

How is it Diagnosed?

Strong circumstantial evidence of cancer can be attained from x-rays, blood tests, ultrasonography, the pet's physical examination and medical history. Most cancers, however, will require a biopsy (a removal of a piece of tissue) for confirmation that cancer exists and to grade the level of severity from benign to aggressively malignant.

Is Cancer Preventable?

Unfortunately, the cause of most cancers is not known and, therefore, prevention is difficult. Early detection and treatment are the best ways to manage cancer in pets.

Common Types of Cancer in Pets

Skin – Skin tumors are very common in older dogs, but much less common in cats. Most skin tumors in cats are malignant, but in dogs they are often benign. Your veterinarian should examine all skin tumors in a dog or cat to determine if any are malignant.

Breast – 50% of all breast tumors in dogs and greater than 85% of all breast tumors in cats are malignant. Spaying your female pet between 6 and 12 months of age will greatly reduce the risk of breast cancer. Surgery is the treatment of choice for this type of cancer. Follow up treatment may be recommended.

Head & Neck – Cancer of the mouth is common in dogs and less common in cats. Signs to watch for are a mass on the gums, bleeding, odor, or difficulty eating. Since many swellings are malignant, early, aggressive treatment is essential. Cancer may also develop inside the nose of both cats and dogs. Bleeding from the nose, breathing difficulty, or facial swelling are symptoms that may indicate cancer and should be checked by your veterinarian.

Lymphoma – Lymphoma is a common form of cancer in dogs and cats. It is characterized by enlargement of one or many lymph nodes in the body. A contagious feline leukemia virus can be the cause of lymphoma in some cats. Chemotherapy is frequently effective in controlling this type of cancer.

Feline Leukemia Complex – The feline leukemia virus is contagious among cats and will occasionally cause different types of cancer. It is not contagious to humans. While a great deal of research is ongoing, no consistently effective treatment is presently available for virus-positive cats.

Testicles – Testicular tumors are rare in cats and common in dogs, especially those with retained testes. Most of these cancers are preventable with castration (neutering) and curable with surgery if done early in the disease process.

Abdominal Tumors – Tumors inside the abdomen are common but it is difficult to make an early diagnosis. Weight loss or abdominal enlargement are signs of these tumors.

Bone – Bone tumors are most often seen in large breed dogs and rarely in cats. The leg bones, near joints, are the most common sites. Persistent pain, lameness, and swelling in the affected area are common symptoms of the disease.

Many of the above signs are also seen with noncancerous conditions but they still warrant prompt attention by a veterinarian to determine the cause. Cancer is frequently treatable and early diagnosis will aid your veterinarian in delivering the best care possible.

How is Cancer Treated?

Each type of cancer requires individual care and may include a combination of treatment therapies such as surgery, chemotherapy, radiation, cryosurgery (freezing), hyperthermia (heating) or immunotherapy. Once you have a diagnosis, your veterinarian will discuss the best treatment option(s) for your pet. In some instances, your veterinarian may refer you to a board-certified oncologist (cancer specialist) depending upon the recommended course of treatment.

What is the Success Rate?

This strongly depends upon the type and extent of the cancer, as well as the aggressiveness of therapy. Some cancers can be cured and almost all patients can be helped to some degree.

Your veterinarian will have a better
chance to control or cure your pet's cancer if it is detected early.

This brochure was developed with assistance from the Veterinary Cancer Society.

10 Common Signs of Cancer in Small Animals

  1. Abnormal swellings that persist or continue to grow
  2. Sores that do not heal
  3. Weight loss
  4. Loss of appetite
  5. Bleeding or discharge from any body opening
  6. Offensive odor
  7. Difficulty eating or swallowing
  8. Hesitation to exercise or loss of stamina
  9. Persistent lameness or stiffness
  10. Difficulty breathing, urinating, or defecating

Resources for More Information
American Veterinary Medical Association

American College of Veterinary Internal Medicine

Veterinary Cancer Society

The American Veterinary Medical Association (AVMA), established in 1863, is a not-for-profit association representing more than 74,000 veterinarians working in private and corporate practice, government, industry, academia, and uniformed services. Structured to work for its members, the AVMA acts as a collective voice for its membership and for the profession

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