Your Pet and Cancer

What is cancer?
Cancer is the common name given to all the various forms of malignant tumours. A tumour is a mass of cells that are growing out of control. There are two main types of tumours.

Malignant tumours or cancer are the most aggressive; they invade into the surrounding tissues and have the ability to spread to other parts of the body. It is this ability to produce secondary tumours that makes them so life threatening.

Benign tumours only grow locally and never spread. They can however cause serious problems just because of their physical size or position.

What should I do if I find a lump on my pet?
Not all lumps turn out to be tumours but it is important to ask your vet to have a look when you first notice one. A small tumour, even a cancer, is more likely to be cured if it is treated early. A biopsy may be necessary to determine the exact nature of the lump. “Let’s wait and see” is not a good option.

How can tumours affect the patient?
This depends upon where the tumour is and what type it is. When small, most tumours do not cause a problem; only when they are large do they affect the patient but by this stage they may be untreatable. As a general rule, malignant tumours (cancers) are more life threatening than benign tumours because of the risk of spread throughout the body.

There are many different types of cancer and each behaves in a slightly different way. It is therefore important to have a sample of the tumours sent for examination by a pathology laboratory.

The cause of Cancer in Cats and Dogs

The scientific basis of cancer
Every cell of the body is normally under very strict control imposed by the body as a whole. Very occasionally, a cell acquires the ability to divide and grow outside this normal control and a cancer develops. This happens when a number of genes within a cell change or mutate. Mutations occur in all of us all the time – in deed without mutations, evolution could not have occurred. Most of the time, these mutations come to nothing but occasionally they cause the cell to go wrong and develop into cancer.

Known causes of cancer (“risk factors”)
For an increasing number of human cancers the cause is known. Some of these risk factors are smoking (lung cancer), certain viruses (cervical cancer) and ultra-violet sunlight (skin melanoma). In addition, certain genes that are present in families have been identified.

In dogs and cats, there are only a few known risk factors for cancer. In cats, the virus known as Feline Leukaemia Virus (FeLV) is a definitive trigger for certain cancers (feline lymphoma and leukaemia). However, not all cats that are infected by FeLV will develop cancer and, conversely, not all lymphomas in cats are induced by FeLV infection.

Another example of a cancer, for which there is a known cause, occurs in white-faced cats that sit out in the full sun. The relatively hairless pink areas of the ear tips, eyelids and nose are prone to sunburn which can progress to skin cancer.

Breed related cancers
Certain breeds of dog appear to be susceptible to specific tumours. This may be related to the characteristics of the breed or due to a genetic predisposition. Bone cancer is more common in giant and large breeds such as Great Danes, Irish Wolfhounds, Rottweilers, and St Bernard’s. This is thought to be related to the rapid growth characteristics of the adolescent pup although there is also evidence for a genetic susceptibility in some of the giant breeds.

For example, Boxers have a relatively high incidence of tumours of the skin and the brain. Bernese mountain dogs appear to suffer from a variety of malignant cancers that tend to affect a younger age group than other dogs as a whole. Similarly Flat-coated Retrievers tend to have a relatively high incidence of cancer which behaves more aggressively than in other breeds of dog. These and other breed related tumours are highly suggestive of a widespread genetic susceptibility for the specific cancer associated with the breed. However, truly hereditary cancers (i.e. that are passed down in certain lines) are rare in dogs.

Further research will identify specific causes of cancers in dogs and cats and may lead to novel ways of treating them. More importantly, as the specific causes become known, specific ways of preventing that cancer may be possible.

You can contact us at
Animal Cancer Trust
5 Flag Business Exchange, Vicarage Farm Road, Peterborough, Cambs PE1 5TX
08701 644225
www.animalcancertrust.org.uk
info@animalcancertrust.org.uk

Registered charity no. 1094779 Animal Cancer Trust is a Registered company limited by guarantee in England & Wales no. 04434009. The registered address of the company is Lacon House, 84 Theobald’s Road, London WC1X 9AA. Please use address above for correspondence.