Health & Medical

Your hand runs down the dog's side while you are watching television, and there it is. A small firm lump under the skin that definitely was not there last month. The rest of the evening is spent quietly panicking and searching the internet, which is the worst possible source of reassurance.

Here is the useful truth. A great many lumps in dogs and cats are entirely benign. But no vet on earth, no matter how experienced, can tell you which category a lump belongs to by feeling it. That is not a failure of skill; it is simply not possible. Benign fatty tumours and aggressive mast cell tumours can feel identical.

The lumps you meet most often

Lipomas are soft, movable fatty deposits under the skin, common in middle-aged and older dogs, especially overweight ones. They feel like a squashy marble that slides under your fingers. Most are harmless and simply monitored. Occasionally one grows large enough to interfere with movement, or an infiltrative variant grows into muscle, which complicates removal.

Sebaceous cysts are blocked oil glands, firm and often slightly raised, sometimes discharging a thick grey material. They can become infected and inflamed but are not dangerous in themselves.

Histiocytomas turn up on young dogs, usually under three, as small raised red button-like growths on the head, ears or legs. They look alarming and often regress on their own within a couple of months.

Warts and papillomas are viral and common in young and elderly dogs, often around the mouth.

Abscesses, especially in cats, appear suddenly as hot painful swellings, usually after a bite from another cat. These need veterinary treatment.

Mast cell tumours are the great imitators of canine oncology. They can look like anything: a small raised bump, a soft lump that could pass for a lipoma, a red irritated patch. They may change size day to day, sometimes swelling after being handled. Boxers, Boston Terriers, Pugs, Bulldogs and Labradors are predisposed. This is the single best argument for testing every lump rather than eyeballing it.

Soft tissue sarcomas are firm, often fixed to underlying tissue, and grow slowly but invade locally. Mammary tumours appear along the mammary chain in unspayed or late-spayed females and are roughly half malignant in dogs, and much more likely malignant in cats.

Features that should move you up the queue

Use a simple mental checklist. A lump is more concerning if it is growing quickly, if it is firmly attached to underlying tissue rather than moving freely, if it is ulcerated, bleeding or weeping, if it is painful to touch, if it changes in size or appearance, or if it appears alongside weight loss, lethargy or reduced appetite.

Location matters too. Lumps on the legs, feet, face and near joints are harder to remove with adequate margins, so early diagnosis is more valuable there. Any lump in a cat deserves more suspicion than the same lump in a dog, because a higher proportion of feline skin masses are malignant.

That said, plenty of malignant tumours are small, slow and painless. Absence of worrying features is not proof of safety.

The test that ends the guessing

Fine needle aspiration is quick, cheap and usually needs no sedation. The vet inserts a small needle into the lump, draws out a few cells, sprays them onto a slide and examines them, or sends the slide to a pathologist. Many results come back within a day or two.

For a lot of lumps this is definitive. Fat cells mean a lipoma. Mast cells have distinctive granules and are recognisable immediately. Where the sample is inconclusive, or where the cell type needs grading, a biopsy is the next step, taking a piece of tissue or removing the whole lump for analysis.

The cost of an aspirate is trivial compared to the cost of treating a tumour that was left for eight months because it looked like a fatty lump. Ask for it. Any good vet will suggest it anyway.

Checking your pet properly

Do it monthly, and make it part of something the pet already enjoys, like a grooming session or an evening cuddle.

Work systematically with flat palms, starting at the muzzle and moving over the head, around the ears and under the jaw. Feel down the neck, then along the shoulders, chest and front legs. Move along the back and flanks, then the belly and mammary area, then the hips and hind legs, and finish with the tail and around the anus. Do not forget between the toes and the pads, which is where owners most often miss things.

Check for swellings in the lymph node regions: under the jaw, in front of the shoulders, in the armpits, in the groin and behind the knees. Enlarged lymph nodes in several places at once always warrant prompt investigation.

Write down what you find. A simple body map with dates, locations and sizes measured with a ruler is worth more than memory. It answers the question your vet will inevitably ask, which is whether the lump has changed, and it stops you from panicking about a lump you have actually known about for two years.

What happens next

If a lump is benign and not causing problems, the plan is usually monitoring. Measure it every month and report any change.

If it needs removing, surgical margins matter enormously. Removing a mast cell tumour with generous margins the first time gives a far better outcome than shelling out the visible lump and having to go back for a second, larger surgery in scarred tissue. This is why the diagnosis before surgery is valuable; the surgeon plans differently depending on what it is.

Staging may follow for malignant tumours: checking local lymph nodes, chest X-rays or abdominal ultrasound to look for spread. It sounds daunting, but it determines whether surgery alone is likely to be curative.

Treatment options in veterinary oncology have expanded considerably. Surgery remains the main tool, with radiation and chemotherapy available, and targeted drugs now exist for certain tumour types. Chemotherapy in animals is dosed for quality of life rather than maximum tolerated intensity, and most pets tolerate it far better than people expect.

The overwhelming majority of lumps turn out to be nothing. But early detection is one of the few genuine advantages owners have, and it costs nothing more than a monthly ten-minute check with your hands.