Cancer in Cats: Types, Symptoms and Prevention

You may be surprised to learn that one in five cats will develop cancer at some point in their lifetime. Whilst this is not as high as the rate seen in dogs, it is still of great concern. Cats tend to hide the fact that they are ill. It is a survival mechanism left over from their days as wild animals. Unfortunately, this means that many feline cancers are well-advanced before the cat owner has noticed that anything is wrong. As with human cancer, the later the cancer is diagnosed, the more advanced it is likely to be and this makes treatment more challenging. The prognosis (outlook) for the kitty will not be so hopeful.

Here is a quick guide to the most common types of cancer in cats and to the symptoms that you should look out for. There’s also some useful information on what you can do to prevent cancer in cats.

Common Cat Cancers: Types and Symptoms

Cat Lymphoma

Lymphoma is the single most common cancer in cats. It is a cancer of the blood which causes one type of white blood cell (the lymphocytes) to multiply rapidly and without control. It is mainly caused by the Feline leukemia virus (FeLV) but now that there is a vaccine available against this virus which does prevent some, but by no means all, cases.

Typically, the disease presents in one of four forms and each of them attacks different organs and causes different symptoms. They are:

• Alimentary feline lymphoma. This is the most common form and attacks the gastrointestinal tract (stomach and intestines), liver, abdomen and the lymph nodes in that area of the body. Cats aged 9-13 years of age are most often affected but the Feline leukemia virus is rarely the underlying cause so vaccination will not prevent it. The most common symptoms to look out for are poops that look dark black and are sticky, obvious blood in the poop or in the litter tray, constipation, diarrhoea, severe fatigue, vomiting and weight loss.
• Mediastinal feline lymphoma. This affects the lungs and the space between the lungs and the ribs as well as other areas within the chest cavity and the lymph nodes in that area. It is mainly caused by the Feline leukemia virus so a vaccine can help to prevent it. The signs to look out for include: excessive coughing, loss of interest in food and weight loss as well as breathing with the mouth open.
• Multicentric feline lymphoma. This form of the disease can affect lymph nodes in multiple areas of the body and in several organs. It is often associated with Feline leukemia virus. Typical symptoms include depression and extreme lethargy with a loss of appetite and associated weight loss. You may also notice that your cat has swollen lymph nodes where their front limbs meet their body, in their jaw and in their groin region.
• Renal feline lymphoma. The kidneys are affected and your cat will typically suffer from weight loss and digestive problems such as vomiting. You will also probably notice that they are both drinking and peeing more often and seem generally weak.
• Solitary feline lymphoma. Any location of the body can be affected. The types of symptoms and the prognosis will depend on which structures and organs are affected.

Squamous Cell Carcinoma

Squamous cell carcinoma (you may see it written as SCC) is a version of skin cancer that is most often seen on the areas of the skin that are exposed to sunlight. Therefore, it is often seen on the ears, the nose and the eyelids. It is caused by sunlight triggering a mutation in the DNA of the skin cells which causes them to multiply abnormally. It is most prevalent in white cats and in cats that live in sunny climates.

There is another form of SCC that develops in the mouth and accounts for around 1 in 10 of all cat cancers. This is an aggressive form of cancer and the prognosis is not good. However, new treatments are being discovered all the time and there are many ways to improve the quality of life for a cat diagnosed with SCC.

Here’s some information on the symptoms that you should look out for:

• Feline squamous cell carcinoma of the skin. You need to be especially vigilant for symptoms in white cats, cats with thin hair and cats that enjoy prolonged periods of sunbathing. Keep an eye on their nose and on their ears. Squamous cell carcinoma of the ear usually starts as a black crust which looks fairly innocent. However, it spreads along the ear and makes it look like a shriveled, black cauliflower. The cancer is similar to human cancer caused by excessive exposure to the sun.
• Squamous cell carcinoma of the mouth. This is a hard cancer to diagnose because the symptoms start inside the mouth where they are not visible. Cats rarely co-operate when you try to have a good look in their mouths. Early symptoms can include bad breath and excessive drooling but these can also be signs of dental problems. If your cat has these symptoms, do not assume that their teeth are causing the problem. Always get them checked over by your vet. Eventually, the disease will make it hard for your cat to eat and you may notice that they are losing weight. If the cancer is in the jaw region of the mouth, you may notice this area becoming firmer and larger.

Fibrosarcoma

As the name suggests, Fibrosarcoma is found in the connective tissue. It is an aggressive form of feline cancer and it is usually treated with radical surgery which may be supported by radiation and chemotherapy. It is the most common form of malignant soft tissue cancer in cats which means that it can spread to other parts of the body. The first tumor may also grow rapidly.

In terms of symptoms, the most obvious one will be a lump just under the surface of the skin which may cause pain when it is touched and could feel fleshy or firm. It does not usually cause an ulcer and rarely bleeds. It may affect the local lymph glands and can spread to other parts of the body where you will also notice lumps. When the fibrosarcoma is advanced, it can cause loss of appetite, dehydration, pain, lethargy and bleeding from the mouth.

There is controversy surrounding the cause of fibrosarcoma. A particular type of feline sarcoma has been named feline injection-site sarcoma because it is found in the neck and shoulder region where vaccinations and other injections are usually administered. In fact, almost half of all feline fibrosarcoma tumors are found in this area and a further quarter are found in the chest or flanks. It is thought by some experts that injected vaccines and injections of corticosteroids, antibiotics, insulin and subcutaneous fluids are causing them. Although the rate of cancers caused by injections is quite low (probably around 1 case per 10,000 to 30,000 vaccinations), vets try to limit the number of injections that they give to cats. Other vets prefer not use vaccines that contain aluminum as there is some research to suggest that it causes irritation and that might increase the likelihood feline injection-site sarcoma developing. In reality, there are probably more risk factors for this cancer which have not yet been discovered.

Preventing Cancer in Cats

There is considerable research underway into the causes of cancer in cats. The hope is that many cases of feline cancer will be prevented in the future.

Preventing Feline Lymphoma

Given the association between feline lymphoma and exposure to the FeLV infection, most vets recommend the FeLV vaccination as a good way of preventing this cancer. It is not 100 % effective and some cats who have been vaccinated will still go on to develop feline lymphoma. This is because there are other causes that have not yet been discovered. There is no need to have all cats vaccinated. Cats who live entirely indoors and who never have contact with other animals are rarely exposed to the virus and do not need to be vaccinated. Getting a FeLV infection makes a cat six times more likely to develop feline lymphoma.

There are some other things that you can do to prevent your cat from getting this type of cancer. Some recent research has shown that cats who are regularly exposed to tobacco smoke are more likely to develop lymphoma in their gastrointestinal tract. Therefore, vets advise that cats live in a smoke-free environment. Of course, this is better for your own health as well.

Preventing Squamous Cell Carcinoma Prevention

As many cases of squamous cell carcinoma are caused by exposure to sunlight, this is tricky to prevent! Keeping cats indoors would be one possibility but this does not suit all cats or owners.

Research has shown that you can help to prevent squamous cell carcinoma of the mouth in your cat by preventing them from being exposed to tobacco smoke. Several studies have shown a link between tobacco smoke exposure for five years or living with a smoker and squamous cell carcinoma in the mouth of cats. It is thought that the carcinogens (substances that cause cancer) settle from the air onto the cat’s coat. Then, when they groom themselves, it is transferred into their mouths and causes cancer.

Preventing Fibrosarcoma

The main advice regarding prevention of fibrosarcoma relates to vaccination. You may not wish to have your cat vaccinated unless they are realistically at risk of contracting the disease in question. If you have a low-risk cat, you may wish to reduce the frequency of vaccination to around three years to cut down on the number of injections that they receive. There are also new protocols for some vaccinations which require them to be administered in the hind legs.

It is not unusual for cats to develop a small lump just after a vaccination. However, if they have a lump at the vaccination site that does not get better in a couple of weeks, it is important to get it checked over by your vet.

General Advice for Cat Cancer Prevention

The most important message here is to not panic. There are many cat cancers that cannot be prevented. It is likely that some cats are simply more susceptible than others because of their genes as is the case for humans.  However, if you would like to take some steps to reduce the risk of cancer for your kitty, here are some general suggestions.

• Spaying/neutering. In female cats, spaying drastically reduces their chances of developing mammary (breast) cancer. If you spay your female cat before her first heat cycle, it reduces the likelihood of her getting mammary cancer to almost zero.
• High-quality diet. This will boost your cat’s health and strengthen their immune system which are important factors in preventing all cancers. Diets rich in fatty acids such as EPA and DHA are thought to prevent cancer so look out for these on cat food labels.
• Avoid over-feeding. Obesity is a risk factor for cancer in many animals. Fat is part of the endocrine system and when there is too much fat, hormones can be released which trigger an inflammatory response and can lead to cancer.
• Stop smoking. Exposure to secondhand tobacco smoke from humans can trigger a number of cancers in cats. Avoid smoking around your pet but ideally you should stop altogether.
• Be careful with chemicals. Household and garden chemicals should be used with caution. Keep your cat inside when you are applying pesticides in the garden. Speak to your vet about the safest way to control cat fleas and other parasites.

Vigilance is very important when it comes to feline cancer. Have your cat tested for viruses that cause cancer. If you have any concerns at all, take your cat to the vet because early detection and treatment give your kitty the best chance of recovery.

Sources:

1. E. Gregory MacEwen, Spontaneous Tumors In Dogs And Cats: Models For The Study Of Cancer Biology And Treatment, Springer
2. Claire M. Cannon, Cats, Cancer and Comparative Oncology, MDPI