Pete the Vet: What to do if your pet has a lump

Harmless wart or dangerous cancer? 'Just monitor it' could be the most dangerous advice of all
Pete the Vet: What to do if your pet has a lump

If you find a lump on your pet, the best advice is to go see your vet. 

When I qualified as a vet, back in 1985, treatment of cancer was simple. If a lump was growing fast, or if it was bothering the animal (itchy, bleeding, or painful), or if it was in a particular location known to have a higher risk of malignancy, then the recommendation would be surgical removal. Other than that, lumps and bumps were generally ignored, or the advice was “just monitor it”.

In 2021, cancer specialist vets would now say that these words (“just monitor it”) can be the most dangerous advice of all. If there is a small, highly malignant lump, the sooner it is surgically removed, the better. Leaving it alone, letting the lump grow and become more established, is definitely not recommended.

So what should you do if your pet develops a lump? The best advice is to visit your vet for an opinion. There are many types of growths that vets can pass judgement on based on a physical examination and the description from the owner of how the growth has been changing over time.

In other cases, your vet may recommend a simple type of biopsy to find out more about the growth: a technique known as a Fine Needle Aspirate (FNA). This simple procedure can usually be done during that first consultation, in a fully conscious animal. A fine, sharp needle is inserted into the growth, and then the contents of the needle are squirted onto a glass microscope slide. This sample is sent to a laboratory for analysis by a pathologist so that the precise cells from the lump can be identified.

If the cells in the lump are benign (such as fat cells, from lipomas, which are probably the most common lumps seen in ageing pets), then there is no concern, and that old advice of “just monitor it” can be safely given.

If, on the other hand, the cells from the lump have malignant characteristics, suggesting cancer, then a more aggressive approach is needed. Sometimes this may mean immediate surgery to remove the cancer, or in other cases it may mean a full core biopsy, sending off a chunk of tissue to the laboratory for detailed analysis so that surgery can be planned more precisely.

An FNA is like looking at a few crumbs from a cake, while a full biopsy is like looking at a slice of cake. It’s easier to work out what the whole cake looks like from a slice, compared to just crumbs.

As well as making a diagnosis of the type of cancer, vets may want to find out far more about cancerous growths through advanced diagnostic imaging. X-rays are still used to screen animals for the spread of cancer (e.g. to the lungs) but CT and MRI scans may be needed to visualise the precise location, shape and size. This can be an important part of analysing a cancerous growth before moving on to treatment. 


Simple surgery used to be the mainstay of treatment of lumps, and it is still the best approach for many cases. Newer surgical techniques, including skin flaps and grafts, mean that surgery can sometimes be carried out for cancers that would have previously been deemed inoperable.

Other methods of cancer treatment have become widely available, following in the footsteps of more diverse treatment options for humans.

Chemotherapy may be recommended for a wide range of cancers, either alone or as an adjunct to surgical removal. Many owners are initially reticent about subjecting their pets to this type of treatment, because of fears about severe side effects. In fact, vets are very aware of the importance of pets enjoying good quality of life, and chemotherapy is used with care to ensure that any side effects are kept to a minimum.

New chemotherapy agents are continually being developed, and novel ways of using these drugs have been introduced (such as metronomic chemotherapy, which uses smaller amounts of chemotherapy agents, given more frequently).

One example of a game-changing type of chemotherapy is a group of drugs called tyrosine kinase inhibitors, which are used to treat mast cell tumours (one of the most common malignant cancers to affect dogs). These new drugs have two actions: first they kill the tumour cells directly, and second, they interfere with the tumour’s blood supply, which stops its growth in a different way. 

These types of drugs are expensive, but they can offer successful treatment for cases that would otherwise be untreatable.

Irradiation of cancerous tissue in pets is also now possible: specialised radiation beams can be sculpted into the exact shape of the tumour. The radiation kills the cells at its focal point while leaving surrounding healthy tissue intact. This is available in specialised centres, and not yet for pets on the island of Ireland.

Perhaps the biggest single change in cancer treatment for pets has been the emergence of veterinary cancer specialists: vets who spend all their time and energy focussed on treating cancer. These vets are able to learn from detailed research, applying the outcomes from thousands of other cases to your pet, so that you can be given a clear prognosis at the start. 

You can then decide if you want to proceed with treatment with accurate expectations about the details of what lies ahead, including the type of treatment, the cost, and your pet’s expected life span.

Cancer is still a diagnosis to be treated with deep respect, but much can be done to help affected pets. If you do want the very best for an animal, talk first to your vet, and if needed, do consider a referral to a veterinary oncologist.

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