Understanding Feline Cancer

Early diagnosis and treatment are keys to coping with a wide variety of cancers. Note: Mammary cancer is by far the easiest one to prevent.


All cats of all ages — no matter how well cared for and protected — are at potential risk for falling victim to one type of feline cancer or another. If undetected and untreated until it has progressed to an advanced stage, this disease — marked by the uncontrolled proliferation of cells in an animal’s body — is very likely to be fatal.

As is the case with human cancer, however, many feline cancers can be manageable if the signs of the condition are recognized early and the patient is given prompt and expert veterinary care.

Common Signs of Cancer in Cats

Signs indicating that a cat is harboring cancer are numerous and varied depending on the site of the cancer and its stage of development. An owner might notice, for example, an unusual lump or swollen area that doesn’t go away or an open sore that refuses to heal. Mysterious bleeding from the mouth or anus may occur. An affected animal may experience trouble breathing, difficulty in urinating or defecating, uncharacteristic lethargy, reluctance to exercise or sudden weight loss.

“Any part of a cat’s body can be affected,” explains Michael Stone, DVM, a clinical professor of small animal medicine at Tufts. “I diagnose cancers every day in my practice.” Although the precise number of cats that are stricken with cancer each year is unknown, the disease’s frequency of occurrence is high judging by the number of cases handled routinely at veterinary clinics in urban areas across the U.S. Ironically, notes Dr. Stone, one reason that cancer has become a leading cause of death is that “cats are better cared-for these days, they live longer, and therefore have more time to develop this disease.”

The terms cancer and malignant mean virtually the same thing: a mass of abnormally proliferating cells that invades into normal tissue, or spreads through the blood or lymph to distant sites, or both. “Skin lumps are the least likely growths to be malignant,” says Dr. Stone. “They may spread, but typically they just grow slowly and behave in a benign manner.” Far more threatening, he notes, are mammary gland cancer, lymphoma and oral cavity cancer.

In mammary cancer, tumors generally develop beneath a nipple and may eventually spread to cat’s lymph nodes, lungs, liver, adrenal glands, kidney and other areas of the body. The earliest signs of mammary cancer are noticeable lumps in an animal’s breast area, which can often be detected by gently palpating a cat’s underside.

Mammary Cancer: The Most Preventable in Cats

“Some mammary cancer patients have prolonged survival after surgical removal of the growth,” says Dr. Stone, “although post-operative chemotherapy is often necessary.” Of all cancers, mammary gland cancer is the most preventable, since its occurrence can be avoided by spaying a female cat at an early age.

Lymphoma is a malignancy affecting cells called lymphocytes, which are found throughout a cat’s body. It can be the result of infection with the feline leukemia virus (FeLV). Both young and old cats may develop lymphoma, with some evidence suggesting that oriental breeds — such as Siamese, Persians and Himalayans — are at elevated risk. Male and female cats are similarly vulnerable.

Typical early signs of feline lymphoma include enlarged internal organs, diarrhea, vomiting and weight loss. If untreated, the disease will inevitably spread throughout an animal’s body, resulting in the gradual weakening and eventual death. “In most cases,” says Dr. Stone, ” prolonged survival of a patient with this type of cancer requires chemotherapy treatment.”

The Danger of Oral Tumors to Felines

Oral cavity cancer produces tumors that affect the superficial lining of the mouth as well as the bony components of the upper and lower jaw. Signs of this condition include lumps in the oral cavity, bleeding from the mouth, foul breath, loose teeth, apparent pain in eating and drinking, and facial deformity.

“Because oral tumors are frequently undetected until they have become large and invasive, they can be very difficult to treat successfully. This is a particularly bad disease,” says Dr. Stone, “often the worst type of feline cancer. Cats suffering from it typically have great discomfort, and they don’t respond well to surgery, radiation or chemotherapy.”

Skin cancer is also relatively common and usually emerges in the form of small, superficial growths that may invade other tissues and organs in a cat’s body. One common type of this disease is squamous cell carcinoma, which affects the flat, scaly cells in the outer layer of skin and is most often the result of prolonged exposure to sunlight. At high risk for skin cancer are white or light-colored cats with prolonged exposure to direct sunlight; the areas of the body most often affected are those that are lightly pigmented, such as the nose, eyelids and tips of the ears. Outdoor cats who habitually bask in bright sunlight are also at elevated risk.

An array of other less common feline cancers — such as those originating in an animal’s liver, bones or intestines — may also be diagnosed. In fact, notes Dr. Stone, what he terms “low-grade cancer of the intestines” is especially common. “This particular cancer has a long course of development — one to three years — and it typically responds well to treatment. Among the many causes of decreased appetite and weight loss in an elderly cat, I find this to be the most rewarding to treat.”

As for the physical and behavioral signs suggesting that a cat may be harboring a neoplasm of some sort, Dr. Stone says: “Each cancer behaves differently and this behavior will depend on the disease’s location. Signs can be as varied as sneezing in the case of nasal cancer, walking in circles in the case of a brain tumor, vomiting if the cat has stomach cancer or constipation in the case of colon cancer.

“Many cancers are associated with loss of appetite and weight loss, so those signs should never be taken lightly by an animal’s owner. Because most cancers occur in older animals, signs of illness in an elderly cat should be taken most seriously.”

How Cats Are Diagnosed with Cancer

As soon as a veterinarian notices evidence of feline cancer during the course of a routine physical exam, a number of sophisticated diagnostic procedures can be implemented in order to rule out the presence of the disease or to determine which type of cancer is present. In addition to a blood cell count and blood chemistry panel, a veterinarian may perform a cytologic exam by inserting a needle into a suspicious tissue area and withdrawing cells from it for microscopic examination. Or, Dr. Stone points out, the veterinarian may perform a biopsy involving removal of a piece of tissue that will then be studied microscopically.

If a malignancy is diagnosed, the veterinarian will proceed to “stage” the disease, a process that is apt to involve the use of such imaging techniques as X-ray, ultrasound, CT scanning and MRI to determine the extent of the cancer’s spread. Treatment will depend largely on the type of cancer that is diagnosed, says Dr. Stone.

“The three most commonly used treatments are surgery, chemotherapy or radiation,” explains Dr. Stone. “Removal of small growths is frequently done by general-practice veterinarians, while major reconstructive surgery usually requires a specialist’s attention, depending on the location and size of a tumor. Chemotherapy is most commonly performed under the guidance of a specialist, although the administering and monitoring of these medications may be done at certain general practices. Radiation therapy, however, can only be performed under the guidance of a specialist.”


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