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Cancer in Cats

cats & veterinarian

Defining Cancer in Cats

Cancer in cats, medically referred to as “neoplasia,” is defined as a malignant cellular tumor. A tumor, which is an overgrowth of abnormal cells and/or the transformation of good cells into bad cells, can be either benign or malignant. Benign (which is good and means that they are usually harmless), or malignant (which is bad and means that they are invasive and tend to spread from one part of an animal’s body to other areas, which is called “metastasis”).

Malignant tumors almost always eventually cause death. Most cancers are more common in older cats and those that are not neutered or spayed, although lymphoma tends to target younger animals. Cats infected with the feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV) are at an increased risk of developing cancer.

Causes of Cancer in Cats

Cancer is one of the leading causes of death in domestic cats. Technically, cancer is defined as one or more malignant tumors. A malignant tumor is a lump or growth that involves rapid cell division and that spreads through the animal’s bloodstream and/or lymphatic system, ultimately infiltrating remote areas of its body. Many people worry that any and every tumor is “cancer,” including bumps or swellings. This is not the case. Often, these are called “benign” masses, which grow slowly and don’t invade and destroy outlying tissues. Certainly, genetic and environmental factors can influence whether or not a cat gets cancer, as can the natural course of aging. Exposure to secondhand smoke, radiation, chemicals and herbicides can increase a cat’s risk of getting certain types of cancer. Cats infected with the feline leukemia virus (FeLV) or the feline immunodeficiency virus are predisposed to getting cancer. Some of the more common forms of cancer in cats are lymphoma, leukemia, mast cell tumors, squamous cell carcinoma, basal cell carcinoma and soft tissue fibrosarcoma. Each of these can present in multiple ways, with varying frequencies and degrees of severity. Common sites of cancer in cats are the skin, blood cells, mammary glands, lymph nodes, digestive tract and mouth. Despite intensive research in both the companion animal and human arenas, feline cancer is still largely an unpredictable phenomenon that is heavily influenced by hereditary, environmental and other unknown factors.

Preventing Cancer in Cats

Unfortunately, until scientists discover and truly understand what causes cats to get cancer, owners and veterinarians won’t be able to do a lot to prevent it from occurring. Regular veterinary visits can help identify any lumps or bumps on a cat’s skin, in its lymph nodes or in its mouth, so that they can be diagnosed and treated as quickly as possible. Surgery, radiation, cryotherapy, hyperthermy, immunotherapy and chemotherapy are available at certain specialized veterinary clinics and veterinary teaching hospitals. Spaying or neutering can reduce the risk of certain types of feline cancer. Feeding a high-quality, palatable and nutritious diet will help keep cats in good overall health, reduce their risk of contracting infectious diseases and developing other disabling disorders. With prompt diagnosis, aggressive treatment and ongoing supportive care, including pain management and long-term dietary support, many cats with cancer can live comfortable and relatively normal lives.

Special Notes

Early diagnosis of cancer always improves the prognosis. Surgery, radiation and chemotherapy are available at specialized veterinary hospitals to treat feline cancer. With prompt diagnosis, aggressive treatment and ongoing management, including pain management and dietary support, many cats with cancer go on to live long, comfortable, and relatively normal lives.

Effects of Cancer – From the Cat’s Point of View

Our feline friends may not look much like us, but mammals are mammals and cats can suffer from many of the same diseases and other medical conditions that affect people. Unfortunately, cancer is one of them. Cancer is more common in cats than in dogs or other companion animals. It tends to affect middle-aged and older cats most frequently, and also those that have not been spayed or neutered. One exception to this is lymphoma (also called lymphosarcoma), which typically is seen most often in younger cats. Regardless of their age, cats that are infected with the feline leukemia virus (FeLV) or the feline immunodeficiency virus (FIV) have a heightened risk of getting cancer. While they can develop a number of different kinds of cancer, there are several types that seem to affect cats most frequently. These are lymphoma, skin cancer, breast cancer and squamous cell carcinoma of the mouth. Feelings of a cat with cancer, depends on how advanced its condition is and which of its organs are affected. Most cats don’t show any signs of pain, discomfort or distress in the early stages of cancer. However, as the disease progresses, metastasizes (spreads) and starts invading the lungs, kidneys or other vital organs, the animal will become increasingly ill. Cats with late-term or end-stage cancer usually lose their appetite, drop weight, become nauseous and are reluctant to move around or exercise.

Symptoms of Cancer – What the Owner Sees

Owners of cats that have cancerous lesions in their mouth, which almost always involve malignant squamous cell carcinoma, often notice one or more of the following signs:

  • Excessive drooling (ptyalism)
  • Lumps or bumps on the gums, inner cheeks and/or tongue; these often are ulcerated, oozing and bloody
  • Difficulty eating, chewing and swallowing
  • Reluctance to eat or drink
  • Weight loss
  • Bad breath (halitosis)
  • Lethargy

Cats with cancer in their gastrointestinal tract may develop one or more of the following symptoms:

  • Abdominal pain
  • Difficulty eating
  • Vomiting
  • Diarrhea
  • Constipation
  • Bloody stools
  • Straining to defecate (tenesmus)
  • Poor body and coat condition

Female cats that have cancer in their reproductive tract may have vaginal bleeding or other abnormal vaginal discharge. Bone cancer, which is uncommon in cats, can cause swelling and pain at the tumor site and intermittent lameness if it involves bones of the legs. Although primary lung cancer is also rare in domestic cats, other types of cancer often spread to the lungs. Owners of cats with secondary lung tumors may observe one or more of the following signs:

  • Difficulty breathing (dyspnea)
  • Coughing
  • Wheezing or other abnormal breathing sounds
  • Weakness
  • Lethargy
  • General malaise and ill thrift

Cats at Increased Risk of Cancer

Aging cats and intact cats have an elevated chance of developing cancer, as do those infected with the feline leukemia virus or the feline immunodeficiency virus. Cats exposed to secondhand smoke, radiation and certain chemicals may also be at increased risk.

Initial Evaluation

Many cases of cancer are discovered when a cat’s owner or veterinarian feels or sees a lump or bump somewhere on or inside of the cat’s body. Visible skin masses can occur anywhere on a cat’s body but most often show up on the face, nose, lips, mouth (gums and tongue), head, ear tips, back of the torso and/or legs. The most common internal tumors that can be felt (palpated) are those that involve lymph nodes located either under the cat’s front “armpits” or in the groin area near the inner thighs of its hind legs. The other way that cancer is often detected is when a cat is taken to the veterinarian because of a slow, steady decline in its overall health, body condition and energy level, for no apparent reason.

Diagnostic Procedures

A veterinarian who sees a cat with obvious abnormal masses will probably recommend taking a biopsy sample to see what the lump is made of. In many if not most cases, the veterinarian will remove the entire mass rather than only just part of it, trying to get clean surgical margins of healthy tissue all the way around the tumor. The removed tissue will be sent to a laboratory for evaluation by a skilled veterinary pathologist. Sometimes, the doctor will take a sample of the mass using a technique called a fine needle aspirate, or FNA. This involves sticking a sterile needle into the lump and drawing cells and fluid into an attached syringe. The sample will be expressed onto a sterile glass slide and assessed under a microscope. If the cat doesn’t have obvious superficial lumps or enlarged lymph nodes but is just not feeling or acting well, the veterinarian will take blood and urine samples to check how the animal’s key organs are functioning. She probably will also run blood tests for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV). These are relatively simple and inexpensive tests that can be performed at any local veterinary clinic.

Radiographs (X-rays) of a cat’s chest are helpful to determine whether any type of cancer has spread to the lungs. If the cat is limping or has painful swollen joints, radiographs can help identify bony abnormalities. Advanced imaging techniques, such as ultrasound, magnetic resonance imaging (MRI) and computerized axial tomography (CAT) scans, are available at veterinary teaching hospitals and some specialized private veterinary practices. These can be used to identify internal masses.

The results of these diagnostic procedures will guide the medical team’s treatment suggestions and protocols. The laboratory report from the pathology laboratory evaluating biopsy samples is probably the single-most important piece of diagnostic information.

Goals of Treating Cancer in Cats

While a diagnosis of cancer is never good, early detection and treatment of cancer in cats can be remarkably successful. Surgery is usually the treatment of choice, although some types of feline cancer respond better to radiation, biological, chemical or heat-related therapies. Sometimes, the recommended approach is to use a combination of treatments. The primary goal of treating cancer is to eliminate all cancerous cells from the cat’s body. If that isn’t possible, the goal is to put the cancer into remission and make the animal as healthy and comfortable as possible, for as long as possible.

Surgical Treatment Options

Solitary cancerous masses are usually removed surgically. It is extremely important for the veterinarian to excise a wide margin of normal tissue around the tumor. This is called “getting clean margins.” Incomplete removal of cancerous tissue almost always causes the cancer to return, making it increasingly difficult to treat. Sometimes, it may be appropriate to remove masses even if clean margins aren’t possible, such as when the tumors are infected or physically interfere with the cat’s normal activities. The veterinarian will submit all removed tissues to a laboratory, where pathologists will determine the type of cancer involved and whether clean surgical margins were obtained. This information will guide the course of further treatment.

Non-Surgical Treatment Options

If a cat’s tumors are inoperable, other treatment options are available. These include radiation, chemotherapy, heat-based therapy and immunological therapy, among others. Many cancer cells are killed by exposure to high levels of radiation, although radiation can also kill healthy tissue, which is one of its adverse side effects. Chemotherapy involves giving anti-cancer drugs that target and destroy rapidly-dividing cells throughout the cat’s body, including cancer cells. Unfortunately, cancer cells aren’t the only ones that multiply rapidly. Other cells that do this are hair cells and those lining the gastrointestinal tract, which explains why hair falls out and patients often become nauseous when receiving chemotherapeutic treatment. While the goal is to eliminate all cancer cells, it isn’t presently possible to completely isolate healthy tissue from cancerous tissue during these treatments. Sometimes, the veterinarian will recommend multiple therapies, such as combining surgery with radiation or chemotherapy. Heat-based therapies, such as electrocautery and cryosurgery, can be used to remove tumors on a cat’s skin, depending on their size and location. Electrocautery, also called hyperthermy, involves using heat to burn off skin tumors. Cryotherapy involves freezing off cancerous skin masses. Hormone therapy and immunotherapy can help manage some types of cancer. An emerging treatment uses special drugs that are sensitive to particular wavelengths of light. These are injected into the cat together with a substance that targets cancer cells. The tumor is then saturated with light. Like most other cancer treatments, these newer procedures are only available at highly specialized veterinary referral centers.

Supportive Cancer Therapies

Modern cancer management involves far more than surgery, radiation or chemotherapy. Nutritional support, pain management, ulcer prevention, physical therapy and other supportive techniques are all critical components of a comprehensive cancer treatment plan.



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