I've found a lump on my cat — what does it mean?
Any new lump on a cat is worth having checked by a vet, even though most turn out to be harmless — things like fatty lumps, cysts, or a reaction to a bite, scratch or old injection site are all common and usually benign. A vet examination is the only reliable way to tell a harmless lump apart from one that needs treatment, so book an appointment rather than watching and waiting.
Usually not urgent
This is common and often manageable at home — but see a vet if it persists, gets worse, or comes with other changes.
Common, often harmless causes
Fatty lumps, medically called lipomas, are soft, slow-growing and common in older cats, particularly under the skin around the body and limbs. Cysts, which can form under the skin for various reasons, are another frequent and usually benign finding, as are small, firm reactions where a vaccination or other injection was given, which typically settle on their own within a few weeks.
Abscesses — a swollen, sometimes warm or painful pocket of infection — are especially common in cats who go outdoors and get into fights, since a bite or scratch wound can seal over and trap infection beneath the skin. These often need draining by a vet and antibiotics rather than resolving alone.
Why every lump still deserves a vet visit
It is not possible to reliably tell a benign lump from something more serious just by looking at or feeling it, which is exactly why a vet check matters even for a lump that seems small and unbothersome. Some growths that need treatment look identical, in the early stages, to the harmless ones described above.
A vet may examine the lump, ask about how long it has been there and whether it has changed, and in some cases recommend a simple sample be taken to identify what it actually is. This is a routine, low-stress part of cat ownership rather than something to be alarmed by on its own.
Signs that mean don't wait
A lump that is growing quickly, feels hard or fixed to the tissue underneath rather than moving freely under the skin, is painful to touch, has broken skin or is bleeding or discharging, needs a same-day or next-day vet visit rather than a routine appointment booked for whenever is convenient.
The same applies if your cat seems generally unwell alongside the lump — off their food, lethargic, or reluctant to move — since that combination points to something more than a simple, isolated skin finding.
What to check and note before your appointment
Gently note the lump's rough size, whether it feels soft or firm, whether it moves under the skin or seems fixed in place, and roughly how long it has been there. If you are not sure when it appeared, that is fine to say — many owners only notice a lump during grooming or a stroke rather than on the day it started.
A quick photo with something for scale, such as a coin next to it, taken on the day you find it and again if you are waiting a few days for an appointment, can help your vet judge whether it has changed.
Everyday habits that help you catch things early
Regular grooming, even a quick weekly brush, gives you a natural opportunity to run your hands over your cat and notice anything new before it grows. This matters more for cats with thicker or longer coats, where a small lump can be easy to miss under fur alone.
If your cat has an outdoor lifestyle and comes home with a scratch or bite wound, keeping an eye on the area over the following days — rather than assuming it will simply heal — can catch an abscess forming before it becomes painful or infected. A quick daily check for the first week after any obvious scuffle is a simple habit that catches most of these early, before they become painful enough for your cat to hide the area from you.
What can help
Things we stock that owners commonly use alongside a vet’s advice — not a substitute for it.
Leucillin Antiseptic Skincare Spray for Cats & Dogs
A versatile, alcohol-free antiseptic spray that cleans, soothes, and helps protect your pet's skin from bacteria, viruses, and fungi.
From£7.99
Absorbent Cotton Gauze Swabs for Pets – Pack of 100
Highly absorbent, low-lint cotton gauze swabs produced in clean conditions — a practical first-aid essential available in three size and ply combinations.
From£4.49
3M Synthetic Under Bandage Padding for Pets
A soft, breathable non-woven polyester padding layer designed to protect and cushion beneath bandages on dogs and cats.
From£9.49
Wahl Pet Grooming Scissors with Finger Rest
Stainless steel finishing scissors with ergonomic offset handles — perfect for tidying around eyes, ears, mouth, and paws.
£5.49
Common questions
- Are most lumps on cats cancerous?
- No, most lumps found on cats turn out to be benign, such as fatty lumps, cysts, or reactions to an injection or old wound. That said, it is not possible to tell a benign lump from something more serious just by looking, so every new lump should still be checked by a vet.
- How quickly should I get a lump on my cat checked?
- Book a routine vet appointment for any new lump, and treat it as urgent if the lump is growing quickly, painful, hard or fixed under the skin, or if your cat seems generally unwell. There is no harm in getting even a small, soft lump checked sooner rather than later.
- Can a cat bite or scratch cause a lump?
- Yes, a bite or scratch wound that seals over can trap infection underneath the skin and form an abscess, which often appears as a warm, sometimes painful swelling. This is especially common in cats who go outdoors and is usually treated by a vet draining it and prescribing antibiotics.
- What does it mean if a lump is soft and moves under the skin?
- A soft, freely moving lump is often, though not always, a sign of something benign such as a fatty lump or cyst. It is still worth a vet check to confirm, since appearance alone is not a reliable way to rule out anything more serious.
- Can neutered cats still get lumps from a fight injury?
- Yes, neutering reduces roving and fighting behaviour but does not remove the risk entirely, especially in a cat who spends time outdoors. Any swelling that appears after a scrap, whether the cat is neutered or not, is worth checking in case it develops into an abscess.
Related
Sources
Written against guidance published by UK veterinary and welfare organisations. Always confirm specifics with your own vet.
Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.