Diagnosing Cancer in Cats

Most feline cancers occur in middle-aged and older individuals 10 to 15 years of age. Lymphoma is an exception, occurring most often in young cats. The majority of feline cancers are not visible by outward inspection, except for skin and breast tumors. These neoplasms can be detected by inspection and palpation.

The high cancer rate in cats is felt to be at least partly related to the feline leukemia virus and the feline immunodeficiency virus. Common sites of involvement are lymph nodes (lymphoma) and circulating blood cells (leukemia), but any organ or tissue in the cat's body can be affected. Taken together, the feline leukemia virus accounts for perhaps half of all internal cancers, the majority of which are lymphomas. It is also associated with other serious cat diseases, including anemia, feline infectious peritonitis, glomerulonephritis, spinal cord cancers, and toxoplasmosis.

Skin tumors are common in cats. Many skin tumors are not malignant; however, the incidence of skin cancer is still high and accounts for 25 percent of feline cancers. Next in frequency is the breast (17 percent).

Cancer is a condition in which rapid cell division and tissue growth occur at the expense of organ-specific function. For example, a cancer from a cat's kidney is biopsied and found to be a mass of tissue that bears only slight resemblance to normal kidney cells under the microscope. The mass on the kidney does not function as kidney tissue, nor does it help the kidney to make urine. If the cancer goes untreated, it eventually replaces the kidney while simultaneously metastasizing to other parts of the body. In time, through a number of possible events, it causes the cat's death.

Cancer is graded or staged according to the degree of malignancy. Low-grade cancers continue to grow locally and reach a large size. They spread to distant organs late in the course of the illness. High-grade cancers spread early, when the primary tumor is still quite small or barely detectable.

Growths of the mouth account for up to 10 percent of feline cancers. Nearly all of them are malignant (squamous cell cancers). Signs include drooling, difficulty eating, and the appearance of a lump or ulcerated growth involving the tongue or gums. A mouth cancer should be distinguished from an infected mass produced by an imbedded foreign body or string cutting into the underside of the tongue.

Some Feline Cancer Facts

  • 32 percent of all cats over 10 years of age will die from some type of cancer.
  • 25 percent of all feline cancers are skin cancers, with 50 to 65 percent of them being malignant.
  • About 25 out of every 100,000 female cats will develop mammary cancer; 17 percent of all feline cancers are mammary related.
  • Feline lymphoma will strike 200 out of every 100,000 cats, with cats who are FeLV positive being at 60 percent higher risk.
  • 10 percent of all feline tumors are found in the mouth.
  • Vaccine-associated sarcomas occur in 1 in 1,000 to 1 in 10,000 cats.

Looking at these facts, we see that 52 percent, or just over half of all feline cancers, occur in areas that can be examined-the skin, the mammary glands, and the mouth. Frequent at-home examinations can lead to early cancer detection in many cases.

Diagnosing Cancers

Clearly, one of the first diagnostic steps for any cat suspected of having cancer is to run a combination FeLV and FIV blood test. A cancer associated with an immune-suppressing virus presents special challenges in treatment. A blood panel might show an increase in calcium-which is seen in some cancers. A urinalysis might indicate protein loss. Those are relatively easy tests to do, require no anesthesia, and can be done at most veterinary clinics.

X-rays are often the next step. An X-ray may show changes in bones or the spread of a cancer. Ultrasound is helpful for identifying soft tissue growths. MRI (magnetic resonance imaging) and CAT (computerized axial tomography) scans are imaging techniques that will only be found at large veterinary referral centers.

A fine needle aspirate or biopsy may be done to take a sample of the growth for analysis. This may not only identify a cancer but also give an idea of the stage and prognosis. Once the type of cancer is known, a treatment plan can be developed.

This article is excerpted from “ Cat Owner’s Home Veterinary Handbook” with permission from Wiley Publishing, Inc.