Lumps and bumps

Finding a lump on your cat can be a worrying experience. Although most lumps are harmless it is impossible to tell what a lump is simply by looking at it. If your cat has a swelling that lasts for more than a few days always ask your veterinarian to check it for you.

©Jo Morris

There are many different things that can cause swellings: bruising or fluid build-up, abscesses, ticks (small parasites which latch onto your cat’s skin and suck blood, swelling as they do so), and, of course, cancers. If you find any unusual lump or swelling on your cat you should make an appointment for your veterinarian to check it out. Although most lumps are harmless, some can be very dangerous if left untreated. The biggest concern for most people is whether their cat has cancer.

Cancers are divided into two groups:

• Benign – these lumps may grow bigger but do not spread elsewhere.
• Malignant – more aggressive lumps which not only grow but also spread through the body and may affect organs such as lungs and liver. A skin lump may also represent a spread from an internal cancer.

Some benign growths can also cause problems if they continue to grow. Even fatty lumps can grow to a huge size and may cause problems due to their physical size, eg restricting leg movement or pressing on the airways and causing breathing problems. Malignant growths are obviously more worrying – they must be treated before they have spread elsewhere.

Even your veterinarian probably won’t be able to tell whether the lump is cancer or some other kind of swelling just by looking at it. There are some things to look for which may help your veterinarian decide whether a lump on your cat is likely to be benign or malignant:

• If the lump can be picked up in the fingers and moved around it is less likely to be aggressive. Malignant lumps often grow into the tissues beneath the skin, and this makes them more difficult to remove.
• If the lump grows very quickly it can soon cause problems even if it does not spread. Removing a large lump is much more difficult and leaves a bigger wound so fast-growing lumps should be removed while they are still small.
• Malignant lumps often cause a reaction in the tissue around them – if any lump is red, painful when touched or is ulcerated or discharging, it should probably be removed.
• Some cancers produce substances that make animals unwell – if your cat has a lump and shows signs of illness eg sickness, depression or excessive drinking then mention this to your veterinarian when he examines your cat.

If a lump has been present for a long time without causing any problems, it is unlikely to suddenly turn nasty. However, all lumps should be monitored closely. Feel the lump once a month (if you feel it too often you will not notice if it is growing slowly) and keep a note of its size. Ask your veterinarian to measure the lump each year at the time of vaccination and record if it is growing. If the lump changes in any way, ie starts to grow more quickly, is sore or discharging, make an appointment for your veterinarian to check the lump again.

If you find a lump on your pet your veterinarian will want to examine the lump to see if they think it is likely to cause a problem. They will also examine your pet to see if she is otherwise healthy or if there are any other growths elsewhere. Unfortunately it will not be possible to say for certain that a growth will never cause problems just by looking at it. If your veterinarian is concerned, they will take some samples from the lump to try to find out what sort it is. Sampling a lump can be as easy as putting a needle into it to collect a few cells or it may be necessary to take a piece of the lump under anesthetic. These samples can be sent to a pathologist at a laboratory who will be able to tell your veterinarian what sort of lump it is. Once your veterinarian knows this, they will be able to advise you on the best treatment for your pet.

In most cases, the only treatment needed for small growths is to remove them. However, if it is a type of cancer that could spread elsewhere your veterinarian may want to make sure that there is no sign of spread and to do this, they may need to take X-rays, do a CT scan, or perform an ultrasound examination. For some cancers it is also relevant to check the local lymph node by taking a sample with a needle and a syringe. If your cat is old or unwell your veterinarian may want to take a blood sample and a urine sample to check your cat is healthy enough to have an anesthetic.

In human medicine skin lumps are often removed by a doctor using local anesthetic. It is unusual for this to be done in veterinary medicine. It is very important that the whole of a cancer is removed to make sure that it does not regrow. Even if the lump appears very small it may be necessary to cut quite deeply to remove all of it. It is important that your cat lies still during the procedure – if they jump or move the operation will be more difficult and dangerous. It is necessary to give patients a sedative to make sure they stay still and calm, and sedation is no safer than a well-monitored anesthetic. Sedated patients may take many hours to recover whereas the effects of a short anesthetic should wear off quickly in most animals. If you are worried about treatment of your cat mention your concerns to your veterinarian who will be happy to discuss all the options with you.

• Abscesses: most lumps on cats are abscesses (usually due to fighting). Often the abscess will need to be opened and drained and antibiotics may be needed.
• Fatty lumps: fatty lumps (lipomas) are much less common in cats compared to dogs. Lipomas are benign cancers that rarely spread and are often quite slow growing. However, they can become very large over the years and may need to be removed because they cause physical problems.
• Basal cell tumors: these are a type of skin cancer that can occur in cats. They often look like firm round masses about half a cm across. The good news is that most of these are harmless and surgical removal results in cure.
• Injection site swellings: swelling and discomfort at the site of a recent injection or vaccination is most likely to be due to a reaction in the skin. If swelling develops a long time after injection or continues to grow you must ask your veterinarian for advice. If a swelling at an injection site persists for 3 months or longer; is, or becomes, larger than 2 cm in diameter; or continues to increase in size 1 month following an injection, then sampling is recommended.
• Soft tissue sarcoma: soft tissue sarcomas may arise anywhere in the body, but they are commonly associated with past injections (injection site sarcomas) and therefore a common site of development is between the shoulder blades. This tumor type is firm, deeply fixed, painful, and may develop very rapidly because it contains cystic cavities filled with fluid. An extensive surgery is recommended if the tumor has not spread. Radiotherapy may be advised to complete treatment when it is not possible to fully excise the tumor.
• Squamous cell carcinoma: squamous cell carcinomas may look like scabs or ulcerated skin, and sometimes bleed. This tumor develops due to sun exposure of lightly pigmented skin (with white hairs) or areas with sparse hairs such as the nose, or the tip of the ear. This tumor type is locally aggressive and should be removed before it infiltrates too deeply into the skin.
• Mast cell tumors: mast cell tumors are less common in cats compared to dogs. They are a type of cancer that can take on many different appearances and can easily be confused with all sorts of other lumps. Some mast cell tumors are harmless and cause no problems, others are very nasty cancers. It is difficult to tell how a mast cell tumor will behave, and so, removal of the tumor plus histopathological assessment and checking for spread to other parts of the body is recommended.
• Mammary tumors (breast cancer): lumps in the mammary glands of cats are not particularly common and may be relatively harmless but some of the most aggressive types of cancer can also be found here. Around 80% of mammary tumors in cats are malignant. Mammary lumps in male animals are often very nasty. When breast cancer is suspected, removal of all mammary tissue (mastectomy) is necessary. Before removing mammary lumps, your veterinarian will want to check your pet thoroughly to make sure that the cancer has not spread anywhere else.

For more information on the conditions listed, check out the Vetlexicon owner factsheets on these topics.

The most important thing to remember is that most lumps, even cancers, can be cured if they are caught early enough – so always check with your veterinarian if you find anything unusual on your cat. In most cases your veterinarian will be able to reassure you.