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Cancer in pets

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Cancer in dogs and cat, as in humans, is essentially an uncontrolled multiplication of cells. Cancer cells do not pay attention to a dog or cat's normal body systems that control cell growth. This explosion of new cells can take over organs and eat away at normal tissues. Cancer can develop in any organ in any pet, but it is much more common in older animals and in certain breeds.

Of course, not all dog and cat cancers are aggressive. Many are relatively benign, often growing very slowly over a period of years. However, even slow-growing tumors can cause a problem in delicate areas for dogs and cats. For example, a tumor in the head may enlarge and put pressure on a particular area of the brain.

Aggressive tumors are termed malignant, often receiving the medical designation of sarcoma or carcinoma. Malignant tumors can rapidly destroy the tissues in which they start. In addition, they commonly spread to other organs such as the lungs or liver, in a process called metastasis.

Sometimes, the progression of a cancer depends on where it is located. For example, pigment tumors called melanomas are often benign when on the head but aggressive and malignant when on the lips.

Cancer is a disease of aging, so the risk increases as our pets get older. Certain breeds, such as Boxers and Golden Retrievers, are also at greater risk because of their genetics. Cancer can also be caused by viruses (eg, feline leukemia virus), as well as by particular substances known as carcinogens. However, the specifics regarding exactly how and why cancer starts are still something of a mystery.

Signs of cancer often depend on its location, but some signs are seen in many different types of cancer. For example, weight loss with or without a loss of appetite is common. Some pets may slow down or pant and pace, unable to settle down comfortably. Others may have pale gums from anemia, or they may have a fever from the inflammation caused by cancer. Diagnosis often involves a series of clinical tests, including blood tests and x-rays. X-rays are especially helpful to see if the cancer has metastasized to organs such as the lungs.

The prognosis for your pet depends on the type and location of the cancer, as well as on the possibilities for treatment. Surgery to remove a tumor can be the most effective option, especially for tumors that are benign or isolated. Aggressive cancers, leukemias, and cancers that involve more than one location may respond best to chemotherapy or radiation therapy. Your veterinarian can also prescribe medications to ease discomfort and improve appetite and mood.

In many cases, the goal of treatment is often to improve your pet's quality of life for its remaining time, rather than to provide a cure. Your veterinarian will discuss treatment options and prognosis so that you can make the best decision for you and your pet.



What is cancer?

Cancer is an uncontrolled multiplication of cells that do not pay attention to the normal body systems controlling cell growth.  

Do all dogs get cancer?

Cancer is much more common in older animals and in certain breeds (eg, boxers and golden retrievers).

Is all cancer serious?

Some cancers are benign, which means that they grow slowly and are often confined to discrete areas.  Malignant cancers are more aggressive, and can take over organs, eat away at normal tissues, and spread throughout the body.  

How is cancer treated?

Cancer is usually treated by surgical removal, chemotherapy, or radiation therapy.  Two or more of these treatments may be combined to maximize destruction of the tumor and prolong disease remission.  

Can cancer be cured?

In some cases, treatment can provide a cure.  However, for many malignant cancers treatment is aimed only at prolonging and improving quality of remaining life.  

Credit: Written and reviewed by John A. Bukowski, DVM, MPH, PhDand Susan E. Aiello, DVM, ELS
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