A Guide to Lumps on Dogs and Cats — Causes, Symptoms, and Next Steps
That small bump on your pet could be harmless or a warning sign of something symptomatic. Learn what to look out for and what to do next to keep your pet safe and lump-free.
Reviewed by Dr. Elizabeth Hardoon
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STORY AT-A-GLANCE
- To the untrained eye, lumps on your pets' bodies seem normal but some may need urgent attention
- There are also certain canine breeds that are more prone to developing growths, from fatty tumors and cysts to specific cancers such as "mast cell tumors"
- Monthly "lump checks" help you catch new growths early
- Signs like rapid growth, bleeding or oozing, pain, or changes in your pet’s behavior (such as licking or biting at the site) mean it’s time to see your vet
- Early detection, diagnosis, and the right treatment can make a big difference in your pet's long-term health and comfort
There's nothing more unsettling for a pet parent than feeling a mysterious lump on their dog’s or cat’s body during a cuddle or belly rub. Is it something harmless, or the start of something serious?
That moment of uncertainty can be scary, but knowledge is your best tool. The first step is understanding why lumps happen in the first place and what they might mean for your pet’s health.
Why Do Lumps Even Show Up?
While there are many factors, most veterinarians look at an animal’s age, breed, and lifestyle to check what causes lumps to form. Older pets tend to develop more fatty tumors and certain cancers. Some well-loved breeds, like Boxers, Golden Retrievers, and Labrador Retrievers, are more prone to cancerous growths.1
Pets who spend more time outdoors may be at risk for infectious causes of lumps such as scratches, punctures by splinters or thorns and insect or animal bites which can lead to bacterial infections that form lumps under the skin, also known as abscesses or granulomas.
You can’t prevent every lump, but you can lower the odds by scheduling regular vet visits (twice a year for seniors), doing monthly home checks, keeping your pet at a healthy weight, protecting light-coated pets from too much sun,2 and maintaining good grooming to reduce infection risks.
Not All Lumps Are the Same
Just like people can have freckles, moles, or bruises for different reasons, pets can develop many kinds of lumps. Some are slow-growing and harmless, others can invade tissue or spread, and a few are linked to injury or infection. You can't tell which is which just by looking or feeling — only a vet can confirm the type through an exam and lab testing.3
- Fatty or soft lumps — These are usually smooth, squishy, and easy to move under the skin. The most common type is lipoma — a fatty lump found especially in older or overweight dogs and are more likely in certain breeds such as labradors and golden retrievers. They can grow large or appear in multiple spots. While lipomas are typically harmless, some can turn into a rare cancer called a liposarcoma.
- Wart-like or skin growths — Some growths stick out from the surface of the skin and may look like warts, tiny horns, or small moles. These include:
- Papillomas (caused by a virus and often found around the mouth or sometimes on the paws)
- Skin tags that form where skin rubs together or at pressure points
- Overgrowths from oil glands like sebaceous gland tumors4 or keratin cysts
- Cysts or blocked glands — Sometimes, a lump can form when part of your pet's skin, such as a hair follicle or an oil gland gets clogged. When this happens, it can cause swelling and form a bump.
- Lumps that form when oil glands become clogged are called sebaceous cysts, while follicular cysts refer to bumps that form when hair follicles are affected. These growths often feel firm, like a small marble under the skin, and if they break open, they may release a thick white material
- Meibomian gland tumors, which develop on the oil gland at the edge of the eyelid, can irritate the eye and sometimes need to be removed by a vet5
- Mouth and gum growths — Lumps aren't always on the skin; they can also form inside the mouth. It's always good to remember that any lump that affects your pet's appetite and ability to eat or causes them to drool too much needs to be checked by a vet. Here are a couple of oral lumps you should keep an eye out for:
- Epulis a gum tissue growth often caused by a tooth rubbing the gums6
- Oral melanomas are cancerous mouth lumps that can be aggressive and spread quickly7
- Serious cancers — Some lumps are malignant, meaning they can spread quickly, damage surrounding tissues, and threaten your pet's life.
- Mast cell tumors are the most common malignant skin tumor in dogs. They can be found on the surface of the skin or also under the skin
- Fibrosarcomas are firm, deep lumps that may invade surrounding muscle
- Squamous cell carcinomas are often linked to sun exposure
- Angiosarcomas are aggressive tumors that develop in the blood vessels8,9
- Melanomas are more commonly found in pets that have dark colored fur, especially on the feet or toes
- Injury or infection-related lumps — Not all lumps are tumors. For example, abscesses are painful, pus-filled swellings that develop after a wound or bite. Meanwhile, granulomas form when the body reacts to an irritant, such as a splinter or insect bite. These may look alarming but can often be treated once the underlying cause is found.10,11
How to Give Your Pet a 'Lump Check' at Home
While it can be worrying to notice a new growth on your pet's body, the best thing you can do to help them is to always be vigilant about the state of their health. You don’t need to go to the vet — a regular lump check at home can help you identify new growths before they become a bigger problem.12
- Pick a calm time to conduct the lump check — Choose a time when your pet is relaxed and happy, such as after a walk, meal, or play session.
- Use both hands — Work from head to tail, feeling over their chest, belly, legs, underarms, groin, tail base, and between toes.
- Notice the details — Is the lump soft or firm? Smooth or irregular? Does it move under the skin or feel fixed? Is it warm, red, or tender?
- Record your findings — Write notes, take photos, and mark the date when the lump first appeared.13 You can also measure it with a ruler to keep track of its size.
If your pet has more than one lump, make a "lump map" to track size and location over time. Has the lump grown or did it shrink? Has it changed color or shape? Jot all of these down so you can share it with your vet.
When to Call the Vet (and Why Waiting Can Backfire)
Some changes mean a vet visit should be your next step. Call promptly if a lump grows quickly, changes shape, feels firm or fixed in place, becomes painful, turns red or warm leaks fluid, or affects your pet’s ability to walk, eat, blink, or breathe or if your pet starts licking, scratching or biting at it. Many pet parents wait because of myths that seem reasonable at first glance:
- "If it's not painful, it must be harmless" — This idea likely comes from human experience, where pain is a common signal of injury. In pets, some dangerous cancers cause no pain early on.
- "I can pop it like a pimple" — This thinking may come from dealing with harmless skin blemishes in people. In pets, lumps can be deeper or tied to blood vessels, and "popping" them sometimes may risk infection or spreading cancer cells.
- "It will go away on its own" — Because minor bumps from bites or scratches often do fade, owners assume all lumps will do the same. Unfortunately, some aggressive growths, such as mast cell tumors and certain cysts can shrink briefly before getting worse.
If a lump balloons overnight, bleeds heavily, smells foul, or leads to breathing difficulties, seek emergency care immediately.14,15
What to Expect at the Vet
Once you've booked an appointment, your vet will start with a hands-on exam, feeling the lump and checking the rest of your pet's body for other changes. From there, they might suggest a few tests to figure out exactly what's going on:
- Fine needle aspiration (FNA) requires a quick poke with a small needle to collects cells; these will be closely examined under a microscope. This is the most common diagnostic that is performed and can be done during your pet’s exam visit in most cases without sedation.
- A biopsy involves taking a small piece, or sometimes all, of the lump so a lab can give a definite answer. A biopsy involves sedation or anesthesia.
- Imaging tests such as X-rays, ultrasound, or CT scans allow the vet to see inside the lump and check if it has spread to other parts of the body.
- Blood tests look for signs of infection, inflammation, and to see if other organ systems are affected. In early stages of cancer the blood test may be normal, especially with lumps found on or under the skin.
Tip — Bring along your notes, photos, and lump map. It can speed up the diagnosis and help your vet see the full picture.16
Treatment Options for Lumps
Remember, when it comes to any kind of medical care, there’s no one-size-fits-all solution — the treatment depends entirely on what the lump turns out to be. Initially, your vet might recommend for you to monitor the lump and see if there are any changes over time such as the lump growing or starting to bleed or ooze. If the test results, however, identify that it is a serious concern, your vet may recommend these options:
- Surgical removal involves taking the lump out, which is often the choice for cancerous or problem-causing growths.
- Cryotherapy freezes small, surface-level lumps to remove them. This is especially useful for sebaceous cysts on the skin and meibomian gland cysts on the eyes.
- Medications may include antibiotics to fight infection or anti-inflammatories to reduce swelling.
- Chemotherapy or radiation is used for aggressive cancers, sometimes in combination with surgery under the guidance of a veterinary oncologist.17
- Alternative treatments such as acupuncture, homeopathy, herbal therapy and supplements may be recommended to boost your pet’s immune system and reduce tumor growth. Some types of supplements, specifically mushrooms such as turkey tail or coriolus can be beneficial in fighting tumor growth. Your holistic vet can work with you to come up with a tailored plan to help treat your pet’s specific growth or cancer.
The Last Word on Lumps
Every lump tells a story, and you are the one most likely to notice the first chapter. By checking your pet regularly, paying attention to changes, and acting quickly when something feels off, you give them the best chance at a healthy, comfortable life.
Your hands and eyes are powerful tools for early detection — and your instincts are worth trusting. If something new appears, don’t wait. Ask questions, get answers, and be the advocate your pet depends on every single day.
