Cancer in Cats
Cats diagnosed with this dreaded disease can still live happy and active lives.
With the number of cats getting cancer increasing every year, cat owners have to hear about this devastating diagnosis more often than ever before. Every living cell - blood, skin, intestines, glands, nerves, bones, muscles, blood vessels, heart muscle, cartilage, abdominal organs, lungs, etc. - has the possibility of becoming cancerous. Only non-living cells, such as teeth, hair and nails, do not become cancerous. Every day thousands of cells divide so that the body can function normally. If anything goes wrong during cell division, cancer can develop. Simply put, cells that normally divide frequently are more likely to make mistakes and divide abnormally. This is why certain types of cells, such as intestinal and skin cells, are more likely to become cancerous than cells that divide less frequently, such as nerve cells.
With the help of MRI, veterinarians can detect cancer in cats at a much earlier stage. With this technology, the disease can be caught early and treatment can begin very early. This could potentially mean a longer life for a beloved companion and a longer relationship between owner and dog.
What is cancer?
The word cancer scares us more than the word tumor, but this fear is unfounded. Cancer is described as a tumor, the natural consequence of which is death. A tumor is an uncontrolled and rapid growth of cells, usually thought of as a lump or growth, but left to its natural state, a tumor may not lead to death. All cancers are therefore tumors, but not all tumors are cancer.
A simpler way of describing a tumor is to examine its behavior: it is either benign (benign) or malignant (malignant). A malignant tumor will most likely metastasize, that is, spread to other parts of the body. Benign tumors do not spread to other parts of the body. When a tumor is malignant, the first tumor is called the primary tumor. New tumors that have spread from the primary tumor are metastases.
Understanding whether a tumor is benign or malignant.
To determine whether a tumor is benign or malignant, pieces of tissue from the tumor are examined under a microscope, called a biopsy. Once a tumor is found to be malignant, its grade is determined according to the appearance of individual cells. The higher the degree of malignancy, the higher the likelihood of metastasis. Malignant tumors are also classified as early or late metastasizing tumors, which determines when metastases can occur. For example, an early metastasizing tumor is most likely to have created metastases by the time the primary tumor was recognized. Conversely, the spread of a late metastasizing tumor can be prevented if the primary tumor is found and treatment is started to prevent metastases from forming.
Late metastasizing tumors are more likely to be treated before they form metastases, but many of these tumors are still life-threatening. Late metastasizing tumors can also be invasive in their own territory, meaning that the primary tumor invades the surrounding tissues. Therefore, successful treatment of these tumors depends on their location. For example, if the tumor is in a toe, amputating the toe or leg can save the dog's life. But if the tumor is in the mouth or on the face, an operation may not be able to remove the entire tumor. In these cases, radiation treatments may be appropriate to shrink the tumor or reduce its growth rate.
Although benign tumors are much less likely to metastasize, they too can be fatal in some cases. For example, most brain tumors are benign, but they are still life-threatening because they interfere with normal brain function or can cause seizures or coma. On top of that, benign gland tumors can secrete hormones that can cause serious problems, such as pancreatic tumors that secrete high levels of insulin or adrenal gland tumors that produce excessive amounts of adrenaline.
What causes tumors?
While finding a tumor can explain why a cat is sick, diagnosing a tumor raises more questions than it answers. One of the most common questions is: “Why do cats get tumors?” Some scientists emphasize the importance of the immune system in preventing tumors. According to them, the body regularly makes mistakes during cell division, but when the immune system works correctly, the body sees these mistakes and destroys the abnormal cells. As a result, when the body ages and the immune system becomes less effective, an error in cell division goes unnoticed by the immune system and turns into a tumor. This theory partly explains why cancer is more common in older cats.
Although the exact cause of most tumors is unknown, experts agree that a combination of factors, such as genetic predisposition, viruses, age, other diseases or environmental factors such as ultraviolet radiation, diet, body structure or carcinogens, can cause tumors to form.
Carcinogens are substances that directly cause tumors, such as asbestos. While there are no carcinogens that specifically affect cats, carcinogens that affect humans, such as cigarette smoke or pesticides, can also cause tumors in cats.
More tumors than before?
Why are there more cases of tumors in cats? Many people think that there must be some reason for this, as they see that the incidence of tumors in cats is increasing. Tumors are more common, much more than they used to be, but many factors can explain this increase. One of the main reasons is that better nutrition, vaccinations, improved treatment methods, diagnostics and the development of veterinary medicine in general means more older cats, more tumors and cancers than ever before.
Another reason for this apparent increase in tumors may be that the role of cats has changed. In recent years, cats are seen more as members of the family and are better cared for than cats that just roam around. Cat owners are much more attentive to the diagnosis and treatment of cats than in the past, and with the increase in the technological ability to recognize tumors, it is much more possible to diagnose tumors than in the past. In addition, cats that move away from their natural lifestyle and share the same environment with humans are more likely to be exposed to carcinogens and tumor-causing substances.
Recognize the symptoms
The symptoms of tumors are as varied as the types of cells that make up the body. The symptoms depend entirely on which tissue is affected. If a tumor develops on the skin, most cat owners will be able to spot it or see the cat licking the spot frequently.
For tumors in the mouth, the inside of the mouth should be checked frequently and excessive drooling, foul-smelling breath or eating difficulties should be noted.
The appearance of skin tumors can be soft and protruding, like a mole, or ulcerated and reddened, like a wound.
Instead of a bulge, growth or swelling, a cancerous tissue looks more like a part that has been eaten. Many serious cases of cancer are neglected by cat owners and sometimes by veterinarians, who see them as slow-healing sores.
Tumors under the skin are often noticed by owners when they stroke or brush their cat. The majority of lumps under the skin are benign fatty tissue tumors, called lipomas, and do not need to be treated: but dangerous tumors can also form under the skin. For example, breast cancer occurs under the skin in the breast area, and thyroid cancer in the neck.
Subcutaneous lumps in the armpit or behind the knee, in front of the shoulders or under the chin may be a cancer of the lymph nodes called lymphosarcoma, which is common in cats. A lump may also be the first sign of a tumor in a muscle, tendon or connective tissue.
In some cases, the first sign may be a limp or slight change in the dog's gait. A bone tumor is usually accompanied by sudden paralysis, reluctance to walk or play, and a marked pain when the affected area is examined.
Tumors in the abdomen usually appear very slowly and often with symptoms that are not very pronounced, can vary greatly and may even come and go from time to time. Most cats become lazy over time, eat less, lose weight, start vomiting. They may have diarrhea or constipation, or drink excessive amounts of water or, conversely, no water at all, and the amount of urine may increase or decrease excessively. Some cats may show almost no symptoms until the tumor is well developed. Occasionally, an intra-abdominal tumor may be discovered during a routine examination in an otherwise perfectly healthy cat. Some types of intra-abdominal tumors can secrete hormones that can cause symptoms such as hair loss, sudden fainting, reluctance to move or weakness, which may not suggest that there is anything wrong inside the abdomen.
Tumors in the heart or respiratory system can cause an increasing cough, immobility, sudden fainting or difficulty breathing.
Tumors on the nerves affect normal nerve function, so a brain tumor can cause seizures, depression, changes in vision or sudden fainting.
Tumors on the spinal cord often cause coordination disorders, weakness or paralysis.
A secondary effect of most tumors is a condition called cachexia, i.e. the gradual loss of the body's muscle mass. This effect used to be attributed to a lack of nutrition due to the tumor's increasing caloric demand. In recent years it has been reported that it is caused by a hormone called cachectin, which is secreted by the tumor.
On the way to Tehshis
Compared to humans, tumors in cats are more advanced at diagnosis. This difference may be due to the tendency of cats to ignore and hide their illnesses and conditions until they have progressed to the point where symptoms can no longer be hidden. Unfortunately, there is no blood test that can diagnose cancer.
Tumors that cause hormone secretion often cause changes in the blood that can be detected by special blood tests, but in most cases blood tests provide very little information Not every bump or mole on the skin requires a biopsy, because most skin tumors are benign and completely harmless. But some features may warrant a biopsy, and sometimes it is wise to remove a tumor surgically rather than waiting to see if it grows and becomes a problem over time. Any pigmented (brownish or blackish) lump or spot on any part of the body should be biopsied or removed immediately. Any wound in the mouth should be biopsied as soon as possible. The rule of thumb is that any wound anywhere should heal or improve significantly within two weeks; otherwise a biopsy or removal should be considered. Any swelling, sore or flesh mole that changes its appearance rapidly should be biopsied or removed. When in doubt, biopsy. Waiting for a lesion to heal can reduce the chance of cure. Even malignant cancers have a chance of cure if the primary lesion is seen and removed in the early stages of the disease.
Remember that it is cheaper, easier and has a better chance of recovery to remove a small lesion with surgery than to wait to see if it disappears. It will also be more difficult, more expensive and less likely to heal once the tumor has grown. Subcutaneous tumors can often be diagnosed with a method called FNAB (fine needle aspiration biopsy). FNAB is an easy and fairly inexpensive way to take microscopic samples of cells without the need for sedation or anesthesia. It is usually not difficult to hold cats while a fine needle is inserted into the tissue. Samples taken by biopsy and FNAB are sent by the veterinarian to a specialized veterinary pathology laboratory that knows how to interpret tissue samples. If the diagnosis is in doubt, a further examination is carried out. Tumors in other parts of the body can be more difficult to diagnose.
The symptoms of many diseases are similar to those of tumors, so many tests may be needed to make a definitive diagnosis. A tumor in the muscles or bones may be suspected when the cat shows pain when walking. X-rays of the affected area can provide information to support the diagnosis of a tumor, but a biopsy is required for a definitive answer. In many cases, if a tumor is highly suspected, amputation (removal of the leg) may be considered instead of a biopsy. As bone tumors can be extremely painful, amputation not only provides definitive pain relief, but is also the best way to ensure successful treatment. Some experts also believe that biopsies of bone tumors increase the likelihood that the tumor will metastasize, and the time lost waiting for the results of the biopsy increases the likelihood of metastasis. Each case must be evaluated individually.
When performed by experienced specialists, ultrasound examinations are particularly useful for visualizing organs inside the abdomen. This technique allows images to be taken from almost any part of the body. However, although ultrasound can show the location, size or structure of a tumor, a biopsy is still required for a definitive diagnosis.
FNAB on a breast or intra-abdominal mass can be performed with little or no discomfort to the cat and with very mild sedation. Another advantage of ultrasound is that a biopsy or FNAB can be performed during the ultrasound examination, so that the veterinarian can see exactly where the needle is for tissue sampling. This way, not only can a piece of the desired tissue be taken, but also there is no danger of, for example, puncturing a major blood vessel. If X-rays and ultrasound examinations do not show a tumor, surgery may be necessary for diagnosis. If a tumor is found during surgery, a biopsy should be performed if it is not possible to remove the tumor completely. It is not uncommon for the owner and veterinarian to want to put the cat under anesthesia to sleep if a tumor is seen during surgery. Although a tumor may appear malignant and there may be other masses that look like metastases, nature can sometimes be deceiving. If the cat is not in pain, it should wait for the results of the biopsy. There is a possibility that a tumor that looks malignant is really malignant, but then again, tumors that look malignant can sometimes be benign. In short, do not decide to euthanize (put to sleep) unless you have a valid reason. An FNAB or biopsy is always needed for a definitive diagnosis.
Treating tumors
The main method of treating cancer is early detection and correct treatment. There are as many ways to treat cancer in cats as in humans, including surgery, chemotherapy and radiotherapy. A cure may only require removal of the mass, or it may require more complicated methods such as chemotherapy and radiotherapy. For some tumors, surgical removal is the first step in treatment.
This may involve removing a whole tumor, part of the skin, a whole organ (such as the spleen or a kidney) or part of an organ (such as the intestine). Many dog owners are frightened when they hear that a limb needs to be amputated, but considering that the cat will no longer suffer and that the cat can live a very good life with three legs, amputation should always be considered as a treatment option.
After surgical removal of a tumor, chemotherapy can be used to prevent metastases from forming or to shrink existing metastases. Chemotherapy is also a treatment option for tumors that cannot be removed by surgery.
The same chemotherapy used in humans is also used in cats. However, the available chemotherapy drugs have many side effects. However, cats tolerate the side effects of chemotherapy better than humans.
Side effects of chemotherapy include loss of appetite, dizziness, vomiting, diarrhea, infections, kidney damage, liver damage, abnormal blood cells or heart problems. Chemotherapy is best administered by veterinarians experienced in its use and familiar with its side effects. It should never be treated as a simple antibiotic treatment by non-specialists. The results of chemotherapy can be highly successful or highly unsuccessful, depending on the type of tumor being treated, the stage at which treatment has begun and the type, dosage and frequency of chemotherapy chosen.
The goals of chemotherapy are not only to provide a cure, but also to reduce the size and activity of a tumor in order to improve the cat's quality of life and prolong its duration. Chemotherapy can add months or even years to a cat's life.
Radiation therapy is a less common technique used for certain types of tumors. It is usually used for tumors that cannot be removed by surgery. The possibility of its application in our country is very limited. The combination of surgery, chemotherapy and radiotherapy provides the most successful means of improving the quality of life and prolonging the cat's life.
Thanks to advances in veterinary medicine, many veterinarians now specialize in diagnosing tumors. However, in some cases, there are no treatments to restore the cat's health. In such cases, the main goal should be to prevent the cat from suffering and ensure a certain quality of life. The difficult task for cat owners in these situations is to interpret the cat's quality of life and decide when and how to euthanize. A natural death is often not a comfortable death and in many cases the best decision a cat owner can make is to end the cat's suffering. This is the most important decision an owner can make for a beloved pet.
As the number of tumor types being diagnosed and treated increases, so do the cure rates. With timely and appropriate treatment, many dogs diagnosed with tumors can live happy and active lives for months or even years. When faced with this diagnosis, you should ask your veterinarian many questions and decide on the appropriate treatment. A cancer diagnosis no longer means the end of a cat's life.
We would like to thank Prof. Dr. Kürşat ÖZER for his contribution.