You are stroking your dog and your hand finds something that was not there before.
The most common next step is to watch it for a while and see what it does. That is understandable, and it is the wrong move, not because most lumps are dangerous, but because the thing that would tell you takes ten minutes and costs very little.
Nobody can tell by feeling it
This is the point of the article, and it surprises people.
Neither you nor your vet can reliably identify a lump by touch. Soft, movable lumps under the skin are frequently fatty tumours, and mast cell tumours, among the more common malignant skin cancers in dogs, are well known for mimicking almost anything, including a soft, harmless-feeling lump.
There is no texture, no shape, and no location that reliably separates benign from malignant.
So the question is never "does this feel worrying?" It is "what did the sample show?"
The ten-minute answer
A fine needle aspirate is the standard first step:
- A thin needle goes into the lump and draws out cells
- The cells go onto a slide and are examined under a microscope
- About ten minutes, usually no sedation, inexpensive relative to almost any other diagnostic
- Often an answer the same day
It does not always give a definitive result, some lumps need a biopsy for a proper diagnosis, but it very often distinguishes "benign, monitor" from "this needs removing", which is the decision you are actually trying to make.
What to ask for: "Can we aspirate this?" It is a specific, reasonable request, and most vets will do it during the same consultation.
When to go sooner rather than at the next visit
Promptly, for any lump that is:
- Growing quickly
- Changing, shape, colour, texture
- Ulcerated, bleeding, or weeping
- Firmly attached to underlying tissue rather than moving freely
- Painful, or being licked persistently
- New in an older dog
- Changing size intermittently, swelling and shrinking. This is characteristic of mast cell tumours, which release inflammatory substances, and it is one of the more useful specific signs
- Accompanied by weight loss, lethargy, or reduced appetite
Anywhere on the mouth, gums or toes deserves particular attention, masses in those locations behave more aggressively as a group.
What lumps commonly turn out to be
Lipomas. Benign fatty tumours, soft, movable, common in older and overweight dogs. Usually monitored rather than removed, unless they grow large enough to interfere with movement, or sit somewhere awkward like an armpit.
Sebaceous cysts. Blocked skin glands. Benign, sometimes rupture and become inflamed.
Warts. Papillomas, common in young dogs and often self-resolving.
Histiocytomas. Fast-growing, dome-shaped, red lumps in young dogs. Alarming in appearance and usually benign, often regressing on their own, but their speed of growth means they are worth confirming rather than assuming.
Mast cell tumours. The great mimics. Highly variable in behaviour, from readily curable to aggressive, and the reason "it looks harmless" is not a diagnosis.
Abscesses. Hot, painful, often after a bite or puncture. Common in free-roaming and community dogs.
Ticks. Genuinely, a firmly attached tick is regularly presented as a skin lump, and it should be removed properly rather than pulled at.
Enlarged lymph nodes. Under the jaw, in front of the shoulders, behind the knees. These are not skin lumps and warrant prompt attention.
Keep a lump map
If your dog has several, and older dogs often do, this is worth the ten minutes.
Draw a rough outline of a dog and mark each lump, with the date found, the size, and the result if it has been sampled. Photograph each one alongside a coin or ruler for scale.
Why it works: with five lumps, nobody remembers which one was always there and which appeared in March. A map turns "I think this one might be bigger" into a comparison you can actually make, and it is the difference between catching a change early and noticing it eventually.
Recheck monthly, running your hands over the whole dog. This doubles as the routine handling that makes your dog easier to examine at a clinic.
The bottom line
Most lumps are benign. That is a reason to get the answer cheaply, not a reason to skip it.
Do not watch an unidentified lump. Watching is what you do after a sample says benign. Watching instead of sampling means that if it does turn out to be malignant, it has been given months to grow, and the small excision that would have been curative may no longer be the option on the table.
Ask for an aspirate. Ten minutes, no sedation, often an answer the same day.
A lump that swells and shrinks intermittently is worth mentioning specifically to your vet. That behaviour is characteristic of mast cell tumours and is easy to dismiss as coming and going.