It happens to most of us at some time or another. You bend down to give your pet an absent-minded stroke, or a tickle behind the ear, or a tummy-rub perhaps, and your fingers close on something – a bit of pet – that wasn’t there before: a lump.

And of course, once you’ve found it, you can’t un-find it. Your mind begins to whirl. Supposing – just supposing – that the lump is actually cancer?

Well I can’t tell you that it isn’t, I’m afraid; not over the Internet especially. So I would strongly advise that if and when that happens to you, you show it to your vet as soon as possible for their advice. Meanwhile, I have some helpful information that you might find quite interesting.

Not all lumps are cancer

There are all manner of lumps. There are haematomas, where an animal bleeds into the skin but the blood has nowhere to go, so it forms a little swelling in the tissue. There are abscesses, where pus from an infection does the same. There is oedema, where fluid builds up for different reasons. There are also foreign bodies stuck in the fur; there are clumps of fur (that are common between toes); there are insect bites and immune reactions and bits of internal organ that you can feel through the skin and there are lymph-nodes.

A little aside: Lymph Nodes

Lymph nodes are part of the body’s drainage system. The cells in your organs and tissues are all surrounded by fluid – tissue fluid – to keep them happy, and there is a network of vessels (or tubes) a bit like the blood vessels, to transport excess or dirty tissue fluid away. These tubes (the lymphatic system) often lead to a lymph node, which acts like a filter for the fluid from that area (now called ‘lymphatic fluid’). A few of these will drain along bigger lymphatic vessels to a bigger lymph node, And so on.

Anyway, lymph nodes feel like little lumps and if there is an infection or cancer in the local tissue, they tend to get bigger. That’s what you’re feeling when you get a bad cold and the ‘glands’ in your throat swell up. There will be more about lymph nodes later; meanwhile let’s carry on.


So some lumps are cancer, and cancer can be aggressive or benign. But what is a cancer? Let’s have another little aside to talk about that.

What is cancer?

Normal cells don’t live forever. The body makes copies of them by a process called cell division. Copies of cells are always being made and older cells are always dying off. That is the Cell Cycle.

But sometimes, when cells divide, there is a mistake. Some of these mistakes are completely irrelevant, but others lead to a different sort of cell. One that divides (makes more cells) faster than those around it, and this can lead to a lump being formed. Lumps are one manifestation of cancer.

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Is that bad?

Well, it’s not always the end of the world. Some of these lumps are benign and will cause no problems whatsoever. But there are two bad things that cancers can do. They can GROW – that is, get bigger and bigger, as though they don’t know how to stop dividing. They can do this until they are squashing, damaging or obliterating the tissue around them, and stopping the body from working in some way. They can also SPREAD – that is, metastasise. Remember those lymphatic vessels? Cancer cells like to travel along them, and so spread around the body.

Now. Although cancer can spread and metastasise, it doesn’t always do it. There are, of course, lots of different types of cancer; cancer behaves differently in different types of cell. There are many cancers where you wouldn’t feel a lump at all. But a lump appearing out of nowhere is a sign that cells might be dividing out of control and we should check them.

What will the vet do?

Feel the lump, first. They will try to feel where it is – in which tissue – and then they will feel any nearby lymph nodes, to see whether they are obviously enlarged. Then they will offer you some options.

What are the options?

Let’s be clear: no vet can feel a lump and tell you that it’s definitely benign; it’s nice if they find another cause that will explain it. If not, then based on the age, place, behaviour and so on, they might be able to take a guess at how the lump will behave. They might propose that the lump is biopsied and staged.

A biopsy is where a bit, or the whole lump is removed and sent to the lab to be tested. In the case of a whole lump, vets will aim to take a good border of normal tissue around the outside, in case cancer cells are already moving outwards from it. The vet or a pathologist can then look down the microscope to find out more information.

Staging a cancer means working out where it’s up in its own life-cycle: whether or not it has spread yet. This includes feeling lymph nodes to see if they’re enlarged and taking chest x-rays to see if there are metastases. Biopsies can be useful here, too.

Once as much information is known about the lump as possible, a plan can be made. Options might include surgical removal, part-removal, chemotherapy in the case of some cancers, and leaving everything well alone.

What outcome can I expect?

Often, for skin lumps, a very good one – but not always. It all comes down to what the lump is and where it is, and how it behaves. Ideally every lump will be sent to a pathologist for testing. Always ask your vet about possible prognosis (final outcomes) you can expect in advance of any treatment they can perform, and any special care needed afterwards.

Best of Luck.

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