Overview
Lumps and bumps are surprisingly common in cats — especially as they get older. Some are caused by infections or minor injuries, while others are growths under or on the skin. Most turn out to be harmless, but a few can be serious. And because cats are experts at hiding discomfort, it’s important to check them regularly and act early if you spot anything unusual.
What are the different types of cat lumps?
When your vet checks a lump, they’re looking to see whether it’s harmless, or if it’s going to grow or spread. Often, it’s not possible to tell the difference just by looking or feeling. Not every lump is a tumour either. Abscesses, cysts, or fluid-filled swellings can look similar, but need different care. Because of this, vets look at the whole picture — the lump’s size, shape, growth and position, along with your cat’s age and health — and may suggest some tests, like taking a small sample, to be sure.
What are the most common harmless cat lumps?
Some lumps in cats are harmless growths that don’t usually cause problems. They’re often found just under the skin and may only need treatment if they cause irritation, press on nearby tissues or affect movement.
Lipomas (fatty lumps)
Lipomas are benign fatty lumps that form under the skin. They’re usually soft, movable, and painless. They grow slowly and are less common in cats than dogs, most often affecting older cats. Many don’t need treatment unless they become large or interfere with comfort or movement, particularly near a joint.
As more serious tumours, such as liposarcomas, can feel similar, any new lump should always be checked by a vet. Monitoring or surgical removal may be advised depending on how the lipoma changes over time.
Sebaceous and follicular cysts
These are small, benign lumps caused by blocked oil glands or hair follicles, trapping fluid or debris under the skin. They often appear as raised bumps containing a white or creamy material (called sebum). They’re usually painless, but can grow, burst, or become infected if irritated. They’re most common on your cat’s head, neck, or back. Cysts shouldn’t be squeezed. If one keeps returning, grows or becomes sore, your vet may suggest surgical removal to prevent further problems.
Skin tags and nodular hyperplasia
Skin tags are soft, fleshy growths that hang from the skin. They’re uncommon in cats but can appear in older animals or in areas where skin rubs, such as the neck or underarms. Nodular hyperplasia is a scary name, but it refers to small overgrowths of skin or glands that form raised bumps. They’re usually harmless and don’t need treatment unless they become painful, irritated, or change in size or shape.
One skin tag or node might look very different to another — their appearances can range from flat bumps to warty or stalk-like lumps. You’d be surprised how many cat owners might think their cat has a skin tag, but it’s really a tick, nipple, or true tumour. If you’re unsure what a lump is, it’s never a bad idea to have it checked by your vet. Never try to remove a skin tag at home, as this can cause pain, bleeding, or infection.
Warts and papillomas
Papillomavirus-related warts are rare in cats but can occur, especially in older cats or those with weaker immune systems. They often appear as small raised or cauliflower-like growths, most commonly on the head, neck, or feet. Most papillomas are benign and don’t cause discomfort, and some may shrink or disappear on their own. Rarely, they can become sore or ulcerated, especially if on the face. Any wart-like lump that grows, bleeds, changes quickly, or looks unusual should always be checked by your vet.
Basal cell tumours
Basal cell tumours are common skin lumps in older cats. Most are benign, but some can grow large, become ulcerated, or cause irritation. Rarely, they behave more aggressively. They often appear as raised nodules on the head, neck, or shoulders and may look pigmented, cyst-like, or scaly. Surgical removal is commonly recommended, particularly if the lump changes, becomes sore or affects comfort.
What are the most common cancerous lumps in cats?
Not all cancerous lumps in cats look the same. Some grow quickly, while others seem harmless at first. Because cancerous lumps can spread, early diagnosis is important.
Mast cell tumours
Mast cell tumours are one of the most common skin tumours in cats. They often appear as firm, raised lumps and may be hairless, reddened, or ulcerated. They usually appear on the head, neck, or limbs any may grow quickly. Some release histamine, which can cause itching or inflammation and can make the surrounding skin look red and irritated. These tumours can be benign or malignant, and appearance alone can’t tell the difference.
Surgery is usually advised to remove the mass, with further treatment depending on the tumour’s type and behaviour. While most affect the skin, mast cell tumours can also occur internally, especially in the spleen or intestines, where signs may include vomiting or weight loss. The treatment options depend on where the tumour is, what effects it is having and whether it has spread.
Read more: The importance of routine health checks in cats
Soft tissue sarcomas
Soft tissue sarcomas are cancers of connective tissues such as muscle, fat, or fibrous tissue. They often feel firm and solidly attached under the skin and may grow slowly at first, but they can spread into nearby tissues, making complete removal more difficult. Surgery is usually recommended. Often, this surgery will also remove a ‘buffer zone’ of soft tissue, as this reduces the risk of regrowth.
There are several types, including fibrosarcomas and nerve sheath tumours. If a sarcoma forms near a joint or limb, it may cause lameness or movement problems. Early assessment improves treatment options and outcomes.
Rarely, cats can develop aggressive sarcomas at injection sites months or even years after the injection. These are known as feline injection-site sarcomas. These tumours can spread into nearby tissues and may be difficult to remove. They often feel firm and may grow slowly at first. They can follow vaccines or other injections, including long-acting medicines, and are usually seen on the scruff, limbs or flanks.
Lymphoma
Lymphoma is one of the most common cancers in cats, but it doesn’t usually show up as a skin lump. It more often affects internal organs such as the intestines, kidneys, or chest, but sometimes it causes enlarged lymph nodes you may feel when stroking your cat, often under the chin or in front of the shoulder. Signs vary depending on where it develops. Intestinal lymphoma can cause vomiting, diarrhoea, or weight loss, while disease in the chest may lead to coughing and breathing problems. Some types are aggressive, but others respond well to chemotherapy, which can improve both quality of life and survival time. Early diagnosis is important.
Squamous cell carcinoma
Squamous cell carcinoma is a common skin cancer in cats, most often affecting pale or white areas exposed to the sun, including the ears, nose and eyelids. It typically starts as a sore, scab or crusty red patch that doesn’t heal and slowly enlarges. This cancer can also occur in the mouth, where it is usually more aggressive and harder to treat. Cats with light-coloured fur and those that spend time outdoors are at higher risk due to UV damage.
Early detection makes a better outcome more likely, and treatment often involves surgical removal. Sometimes squamous cell carcinomas are treated with cryotherapy. This is a non-surgical procedure where the cancerous cells are removed by cycles of freezing. It’s typically an easier recovery for your cat than it would be with traditional surgery and, depending on the size and placement of the cancer, it can be less expensive too.
Mammary tumours
Mammary tumours are one of the most common cancers in female cats, especially those that haven’t been spayed. Lumps are usually found along the belly or chest near the mammary glands and may feel firm, irregular, or fixed in place. Most mammary tumours in cats are malignant. Spaying before the first or second heat greatly reduces the risk. If found early and removed before spreading, surgery can be effective, though more advanced cases may need further treatment. Any new lump in this area should be checked promptly. Remember, Pet Health Club members get up to 20% off neutering procedures.
Other less common cancers
Alongside more common skin tumours, cats can occasionally develop rarer cancers that appear as lumps. These include melanomas, which are often dark or pigmented and commonly affect the face or mouth, and fibromas, which are usually slow-growing tumours of fibrous tissue. These cancers are uncommon, but some can behave aggressively, so any unusual or changing lump should be checked by a vet.
Are lumps in cats always tumours?
Not all lumps are tumours. Some are caused by infection, injury or inflammation and can feel like growths under the skin. These are common in cats, particularly those that go outdoors or get into fights. Many are minor, but some can become painful or infected, so it’s best to have them checked if they don’t settle quickly.
Abscesses
Abscesses are painful, pus-filled swellings, most often caused by fighting wounds from other cats. They develop when bacteria from teeth or claws become trapped under the skin. The area is usually swollen, warm, and sore, and your cat may seem quieter, lose their appetite, limp, or avoid being touched. An abscess may burst and release a foul-smelling discharge, which can ease pressure but leaves an open wound that can easily become reinfected. Prompt treatment is important and usually involves draining and flushing the abscess, sometimes with antibiotics to clear the infection.
Seromas and haematomas
A seroma is a soft, fluid-filled lump that can appear after surgery or trauma, often near an incision or wound. It’s a collection of clear fluid and is commonly seen after procedures such as spaying, especially if the pet has been overly active. Seromas often look worrying but are usually painless and tend to shrink over a couple of weeks. If a lump becomes red, warm, painful or continues to grow, your vet should check it.
A haematoma is filled with blood rather than fluid and usually follows trauma. In cats, this most commonly affects the ear and is linked to head shaking or scratching, often due to an ear infection. Haematomas can be uncomfortable and may need drainage or surgery to heal properly.
Enlarged lymph nodes
Cats have lymph nodes in several areas, including under the jaw, in front of the shoulders, behind the knees and in the groin. These form part of the immune system and can swell in response to infection, inflammation, or cancer. An enlarged node may feel like a firm, mobile, bean-sized lump under the skin and isn’t always painful.
Causes range from local issues, such as dental disease or skin infections, to more widespread illness, including viral infections or lymphoma. If you notice one or more of your cat’s lymph nodes swelling up, you should see your vet. They’ll assess whether the problem is local or systemic, and figure out the cause.
Injection site reactions
Some cats develop small, firm lumps at injection sites after vaccines or other injections. These are usually a normal immune response and tend to shrink and disappear within a few weeks. Mild swelling or tenderness soon after vaccination is common, particularly in young or slim cats. If an injection site remains lumpy, painful or irritated after two weeks, it’s best to see your vet.
Read more: Feline leukaemia
Foreign body reactions
Outdoor cats can sometimes pick up splinters, grass seeds, thorns, or other debris under the skin. These are most commonly seen around the paws, but can occur elsewhere. The body reacts by forming a local lump, which may become inflamed, sore, or infected over time. These lumps can feel firm or tender and may develop into an abscess or start to discharge. If the foreign material isn’t removed, the reaction can persist or worsen. Treatment usually involves removing the debris and cleaning the area, with antibiotics if infection is present. Any painful or growing lump should be checked promptly.
Ticks
Ticks can attach to cats and swell as they feed, creating a small, round grey-ish lump that’s easily mistaken for a growth. They’re most often found around the legs, ears, neck, or face. Don’t attempt to pull ticks off with your fingers, burn them off, or apply any ointment — this can lead to further harm, and encourage nasty tick juices being squeezed into your cat, making infection with tick-borne diseases more likely. A proper tick remover (or help from your vet) is the safest option. Regular parasite prevention and hands-on checks can help you spot ticks early.
How can I tell if a cat lump is serious?
Many lumps are harmless, but some can point to a more serious issue. Cats are good at hiding pain or discomfort, so changes aren’t always obvious, even if your cat seems fine. It’s a good idea to book a vet check if you notice:
A lump that’s growing quickly
A lump that feels firm, fixed, or deep under the skin
Ulcerated, scabby, or bleeding lumps
Lumps that seem painful when touched
Any lump that changes in size, shape, or texture
A lump near a previous injection site
Other symptoms such as weight loss, low energy, or changes in appetite alongside a lump
Even small lumps can matter, especially in older cats. If you’re unsure, having your vet take a look is the safest next step.
How are cat lumps diagnosed?
To find out what a lump is, your vet will start with a hands-on check, looking at its size, shape, position, and how it feels. Because looks alone don’t always tell the full story, they may suggest one or more tests, including:
Fine needle aspiration (FNA): a small sample of cells is taken with a needle and checked under a microscope. It’s quick and usually doesn’t need sedation.
Biopsy: a small piece of tissue is removed, under sedation or anaesthetic, and sent to a lab. This gives more detailed and reliable results.
Imaging: x-rays or ultrasound may be used to see how deep the lump goes or whether nearby tissues are involved.
These tests help your vet understand whether a lump is harmless or needs treatment, and decide the best next steps for your cat.
How do I check my cat for lumps?
Cats don’t always enjoy being checked over, but regular, gentle checks during grooming or cuddle time can help you notice changes early. Try to:
Run your hands over your cat once a week, focusing on the head, neck, belly, and limbs
Look out for new lumps, scabs, or sore areas, especially where your cat can’t groom easily
Take a photo and measure any lump you find so you can keep track of changes
Keep a simple note of dates, size, texture, and any changes in behaviour
If your cat isn’t keen on handling, keep checks calm and brief, and finish with a treat
Spotting changes early (even when your cat seems perfectly well) can make a real difference.
Cat lumps and bumps FAQs
Can parasites or insect bites cause lumps in cats?
Yes. Ticks, insect bites and stings can cause small, red, or swollen bumps, which may be itchy. Most settle on their own, but it’s best to see your vet if a lump grows, doesn’t go away, or seems painful.
Should every lump on a cat be tested?
It’s not a bad idea, but if a lump is small and staying the same size, you may just be able to keep an eye on it, under advice from your vet. If a lump grows, changes, becomes sore, or returns, your vet may suggest testing — often starting with a fine needle sample.
Can allergic reactions cause lumps on cats?
Yes. Allergic reactions can cause small bumps or swellings, often linked to insect bites or contact with something irritating. These are usually due to inflammation, but any lump that persists should still be checked by your vet.
Do older cats get more lumps?
Yes. As cats get older, they’re more likely to develop lumps — both harmless and more serious. That’s why regular checks become even more important as your cat ages.
Will a vet always remove a lump?
Not always. If a lump looks harmless, stays the same, and isn’t bothering your cat, your vet may simply keep an eye on it. If there’s any doubt or concern, they may suggest testing a small sample to see whether removal is needed.
Why did my vet ask me to track my cat lump’s size and shape at home?
Lumps that change quickly are more likely to need attention. Simple measurements or photos can help your vet see how fast a lump is changing and decide whether further tests are needed.
Do indoor cats still get lumps?
Yes. Indoor cats can still develop lumps, including harmless growths, cancers, allergic reactions, or lumps at injection sites. Regular skin checks are important, whether your cat goes outside or not.
What other signs should I watch for if my cat has a lump?
Changes such as a drop in appetite, low energy, weight loss, or grooming less than usual can sometimes be linked to a lump, especially if it’s painful or internal. Always let your vet know if you notice any of these signs.
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For more help and advice on cat lumps, or if you're concerned about a lump on your cat, have a chat with your local vet. Remember, members of Pet Health Club get two nose-to-tail healthy pet checks a year.
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Medically reviewed by Lizzie Youens, BSc(Hons) BVSc MRCVS
Published on 16/01/2026 • Reviewed on 16/01/2026