Cat & Dog - Nasal Tumours

These notes are provided to help you understand the diagnosis or possible diagnosis of cancer in your pet. For general information on cancer in pets ask for our handout What is cancer. If not already performed your veterinary surgeon may suggest certain tests to help confirm or eliminate the diagnosis, and to help assess treatment options and likely outcomes. Because individual situations and responses vary, and because cancers often behave unpredictably, science can only give us a guide. However information and understanding of tumours in animals is improving all the time.

We understand that this can be a very worrying time and we apologise for the need to use some technical language. If you do not understand anything, please do not hesitate to ask.

What types of nasal tumours are there?

In some cases, chronic inflammation of the nose (rhinitis) leads to proliferation (hyperplasia) and formation of polyps in the nose or throat. These are not cancerous but may need removal. The chronic inflammation is often due to infections with viruses, bacteria and/or fungi and also occurs in animals with a tendency to allergies (atopic animals). Some chronic infections predispose to cancer.

Most cancers originate from the lining of the nose (epithelium). Benign tumours (adenomas) are rare but if they are surgically removable, they are curable. Malignant tumours (carcinomas) are commoner with many different types. All of them invade and destroy adjacent structures. They rarely spread (metastasise) elsewhere in the body. A few carcinomas originate from hormone-producing neuroendocrine cells. These may invade the brain.

A few cancers originate from the supporting connective tissues of the nose (cartilage, fibrous tissue or bone). These sarcomas tend to be less aggressive than carcinomas but can rarely be removed surgically. They may also recur following surgical removal.

Non-cancerous proliferation (growth) of the lymph tissue (which includes the tonsils) forms nodules that physically obstruct air flow. These are common and probably the result of chronic or multiple infections. Cancer of the lymph tissue in the nose and throat is rarer but occurs in cats.

What do we know about the cause?

The reason why a particular pet may develop this, or any cancer, is not straightforward. Cancer is often seemingly the culmination of a series of circumstances which come together for the unfortunate individual.

Chronic inflammation due to bacteria, fungi and viruses may predispose to cancerous change. Viruses have been found in some tumours in cats and farm animals. Environmental factors may also be involved in initiating some cancers. Cancers of the lymphoid cells in young to middle aged cats are often due to infection with viruses (feline leukaemia virus, FeLV).

Why has my animal developed this cancer?

Some animals have a greater tendency (genetic susceptibility) to cancer. Some breeds have far more cancers than others, often of specific types. The more divisions a cell undergoes, the more probable is a mutation so cancer is commoner in older animals. A few tumours need hormones to start growing or to enable them to persist.

Are these common tumours?

Primary tumours of the nose are rare in dogs. They comprise less than 1% of tumours and are estimated to have an incidence of 2.5 per 100,000 dogs. The risk of developing tumours is highest in old dogs but the average age of affected dogs is approximately nine years. They have been observed in dogs less than six months of age. Rough Collies and Shelties have a high incidence of nasal tumours and short nosed breeds have fewer tumours at this site. Half the tumours occur in both nostrils. Tumours in the nose are commoner in cats than in dogs.

Benign tumours (adenomas) are rare. Carcinomas are the most common nasal tumours with sarcomas of cartilage, fibrous tissue and bone in decreasing order of frequency. Lymphoid tumours in this area are rare in dogs but moderately common in cats and usually occur at a younger age than carcinomas.

How will these cancers affect my pet?

Regardless of sub-type, tumours are soft, pale masses that cause compression, destruction and loss of function of adjacent structures. There is usually blood stained or thick, creamy discharge from one or both nostrils. Sneezing, shortage of breath and weeping eyes are possible and at later stages, the face may be deformed and the eyes may bulge. Occasionally, the first signs relate to pressure on the brain with behavioural changes, circling and sight problems.

How are these cancers diagnosed?

Radiography (x-ray) and computed tomography (CT) can often provide a high probability of diagnosis. Radiologically (on xrays), there is usually an increase in density compared with when there's destruction of bone in inflammation. However, distinction of cancer from inflammation is not always possible and definitive diagnosis relies on histopathology (where a sample is sent to a lab for special staining and microscopic examination).

Cytology, the microscopic examination of cell samples washed out of the nose is not reliable and larger pieces of tissue need to be taken for histopathology. Larger samples enable more reliable diagnosis of cancer but sometimes repeated biopsies are needed. Histopathology is done at a specialised laboratory by a veterinary pathologist.

What types of treatment are available?

Surgery and radiotherapy are the only treatments shown to be of benefit. Interstitial brachytherapy, the insertion of radioactive material into the tumour, has given some useful remission. Radiotherapy may prolong survival but not by more than a few months. Surgery often presents problems. The tumours are usually infected and inflamed so antibiotics and anti-inflammatory drugs may make your pet more comfortable.

Can these cancers disappear without treatment?

Cancer rarely disappears without treatment but as development is a multi-step process, it may stop at some stages. The body's own immune system can kill cancer cells but it is rarely 100% effective. Rarely, loss of blood supply to a cancer will make it die but the dead tissue will probably need surgical removal.

How can I nurse my pet?

After surgery, you may be provided with an 'Elizabethan collar' to prevent your pet from interfering with the operation site which needs to be kept clean. Any loss of stitches or significant swelling or bleeding should be reported to your veterinary surgeon.

If you require additional advice on post-surgical care, please ask.

How will I know how the cancer will behave?

Histopathology will give your veterinary surgeon the diagnosis that helps to indicate how the tumour is likely to behave. The veterinary pathologist usually adds a prognosis that describes the probability of local recurrence or metastasis (distant spread).

When will I know if the cancer is permanently cured?

'Cure' has to be a guarded term in dealing with any cancer.

Most nasal polyps persist because they have become mainly scar tissue (fibrosed) so removal should cure them permanently. Lymphoid hyperplasia should become less of a problem as your cat gets older.

Many tumours can have their behaviour predicted by the stage at which they are diagnosed but this is not predictive for these tumours of the nose.

Benign cancers (adenomas) are rare but if they are surgically removable, they are curable. Nasal carcinomas typically grow slowly but they invade and destroy adjacent structures. The neuroendocrine type tend to invade the brain. Distant spread is unusual. Dogs and cats seldom survive more than a year after diagnosis. Carcinomas are more invasive and destructive than sarcomas.

Chondrosarcomas tend to grow by expanding locally. The median survival of dogs with these cancers after a variety of treatments including radiation therapy ranges from 7 to 17 months. Osteosarcomas and fibrosarcomas tend to be more aggressive.

Are there any risks to my family or other pets?

No, these are not infectious tumours and are not transmitted from pet to pet or from pets to people.