Lipomas, Fatty Tumours & Lumps Under Dogs Skin

Updated May 5, 2021

Here I will help you identify a lump found under the skin of a dog.

Tumours and masses cause a lot of concern to dog owners. However, with some basic knowledge, and the right action, there’s nothing to fear.

First though I need to clear up a common misconception.

Do Lumps Appear Overnight?

Many lumps seem to appear suddenly. The good news for dog owners is that this is almost never really true.

But, you say, it definitely wasn’t there yesterday! What’s going on here?

A lump will creep up gradually, ‘under the radar’. Because it changes slowly, it doesn’t trigger your awareness. You’re not looking for problems, so it just hides in the contours.

Then, one of three things happens:

  • it reaches a sufficient size to be noticed
  • the surrounding coat gets a bath or shave
  • your dog loses weight

Now, you can’t stop seeing it. Jeepers, you can even see it across the room.

Trust me on this: definitely see a vet, but the lump could have been there six months. And you want it that way; a slow growing lump is unlikely to be cancerous. It’s the same way you don’t notice a dent or scratch on your car, and then once you see it, it drives you crazy.

Types Of Lumps Under The Skin

Most of the time, a lump under the skin of an old dog is a lipoma, or fatty tumour. However, the biggest mistake is assuming this without testing. It’s no good being right 99% of the time if the other 1% ends up with amputation or worse.

Warning: the idea that you can identify a lump by whether it’s hard or soft, or whether it moves under the skin is false. And at this stage, even the nastiest tumour won’t have any effect on health or behaviour. After this list of common lumps, I’ll show you the only way to tell them apart.

Also visit: a guide to the skin lumps of dogs.

Lipoma

Lipomas are benign tumours of fat tissue. They are most commonly found:

  • in the armpit
  • on the chest
  • on the flank just in front of the hind leg

The picture above shows a large lipoma in the armpit (axilla) and my hand on a smaller one on the chest just behind. It goes to show how hard these lumps are to see.

A lipoma can appear at any age, but most often over 10 years. They grow so slowly that you certainly can’t tell they’ve grown in a month, and usually not even in 3-6 months.

Lipomas are easy to take out and almost never recur after surgery. However, not all need removal as they are painless and slow-growing. Whether we operate depends on five factors:

  1. the position: lipomas in the armpit or on the chest are especially troublesome
  2. the dog’s age: if a dog is 14 there’s not much chance that a small lipoma will trouble them in their expected lifespan
  3. the owner: tolerance of skin lumps and ability to afford surgery vary a lot from person to person
  4. the dog’s health: other illnesses might increase the anaesthetic risk
  5. the speed of growth: rapid enlargement will cause problems just through size and weight alone

Occasionally, a fatty lump isn’t a lipoma, but a liposarcoma or infiltrative lipoma. These are nastier versions of fatty tumours that definitely need removal before it’s too late. You can usually get a clue by how fast they grow.

Fibrosarcoma

dog sarcoma tumour
Sarcomas

This is the lump that’s most often mistaken for a lipoma because it often feels exactly the same: soft, rubbery and round.

Fibrosarcomas are aggressive, invasive cancers that need urgent attention. Just look at the surgical margins necessary for removal and you can see why.

Speed of growth and position are the best clues. If you can tell that a soft lump is growing, think sarcoma. If it isn’t in the typical places for a lipoma, think sarcoma. However, they can occur anywhere.

Mast Cell Tumour

Mast cell tumours are often a raised red lump, but if they grow under the skin they are almost indistinguishable from a sarcoma, and can be just as dangerous. Usually they can be diagnosed from a simple needle sample at the first visit.

Read more about mast cell tumours and their treatment here.

Cyst

dog sebaceous cyst
Sebaceous cyst

A build up of liquid or even solid material under the skin is called a cyst. The most common is a sebaceous cyst, caused by a blocked sebaceous gland. These can grow quickly or slowly, and often burst, releasing a thick brown paste.

You’ll find sebaceous cysts most commonly along the top of the dog from neck to tail.

A soft, painless, cool lump that appears under a surgery site is most often a seroma. This is caused by fluid collecting in the space created by the operation. Seromas can also occur over bony points like the elbow or head after injury.

Cysts rarely need treatment. Sebaceous cysts will grow slowly but normally cause few or no problems. Seromas come up quickly but should go down by themselves over a few weeks.

Abscess

A special form of cyst filled with pus is called an abscess. Abscesses are well-known in cats, but when we see them in dogs there’s usually an underlying cause. Common examples are stick injury, grass seeds or other foreign bodies.

An abscess comes up quickly and is usually soft, warm, and painful. Its appearance prompts us to perform an anaesthetic and carefully explore the cavity.

Lymph Node

dog lymph nodes

Lumps in the places indicated are often caused by lymph node enlargement. If you can feel a lymph node, this is a bad sign, as that means it’s quite large.

Lymph nodes are very firm and immobile. The only common cause is lymphoma or other cancers, but sometimes a single enlarged node might be caused by infection.

Mammary Tumour

dog breast lumps
Firm masses under the nipples of an older entire female dog. The abdomen is enlarged due to pyometra, a uterine infection.

If your dog is female, and has been desexed later in life, consider mammary tumours. These are firm lumps growing anywhere along the mammary chain from armpit to groin. They often feel quite irregular in shape.

Unlike people, mammary carcinoma usually spreads slowly and small lumps can be removed without radical surgery. Desexing at the time will reduce further tumour development but not stop it completely.

Vaccine Reaction

A firm, but vaguely defined lump around 5cm in size sometimes comes up at the site of vaccination. A typical site is on the back of the neck between the shoulder blades. It should be non-painful and follow the vaccination by less than two weeks.

Vaccine associated sarcomas have been reported at the same site but these are very rare in dogs, and usually associated with vaccines not used in Australia.

Other Lumps

Two common lumps often get mistaken for tumours, but are in fact normal.

There’s a salivary gland in the neck behind the jaw that feels a lot like the lymph node just in front. It’s also firm and round, and roughly 2cm in a medium dog. However, it shouldn’t stick out, and the opposite one should feel exactly the same.

A hand-shaped firm mass is often found on the rump of overweight dogs. This is usually a fat pad which feels firmer than usual due to the pelvis underneath. For this to be true, there should be an identical one on each side, though one will stick out more if the dog is not standing straight.

perineal hernia dog
Perineal hernia

There are many other rarer possibilities too numerous to mention, that probably together only make up an extra 1%. Pictured above is a perineal hernia, which occurs in older undesexed male dogs. Inguinal hernia, by contrast, is a bulge in the groin where the leg meets the body.

What To Do If Your Dog Has A Lump

The only way to identify a lump with certainty is with a visit to the vet.

Most vets will start with a fine needle aspiration as shown in the link. This will be able to immediately identify a lipoma or cyst.

Other tumours require further testing. Here we have three choices:

  1. Send the slide of aspirated material to a pathologist. This can be diagnostic but is unreliable as the tissue architecture has been lost.
  2. Schedule an ‘incisional biopsy’, where we only take a small piece and get it analysed. This is the best way as it allows us to plan for a single curative surgery.
  3. Schedule an ‘excisional biopsy’, where we remove the entire mass and get it analysed. Without a wide margin, this will only be curative for very benign lumps and require a second surgery for most others.

The decision we take will depend on many factors. Here are some thoughts we may have:

  • It’s always good to send the slide, but the extra cost might not be justified by its unreliability
  • An excisional biopsy is never a good idea without analysis unless the vet is certain the lump is benign, or there is plenty of loose tissue for a second surgery
  • An incisional biopsy followed by definitive surgery will usually give the highest total cost

The single greatest influence on a successful outcome will be how quickly you choose to get a lump checked. This is especially true in places with poor skin coverage, like the head, legs and tail. No vet likes to see a lump for the first time and think, “I hope this is benign, because if it’s not…”

Related: Common Mouth Lumps | Lumps Under The Eye

Have something to add? Comments are welcome below and will appear within 24 hours.
By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These articles are from a series regularly posted on email and Twitter. Subscribe via email here to never miss a story!

Andrew

25 Replies to “Lipomas, Fatty Tumours & Lumps Under Dogs Skin”

  1. Hi, I have a young male Shiba Inu rescue, about 2 years old. He’s got a toned body, with shorter coat. He’s in very good shape and is neutered. He is also on a grain free, salmon and pea dry kibble diet.

    While he was laying on his side and I was petting him, I noticed a small pea sized soft lump above his shoulder blade on his chest (left side). I immediately panicked. Should I be worried? From what I’ve read, it sounds like a fatty tissue or cyst, but my mind always thinks the worst.

    I’ve never noticed this small lump before, but perhaps it has always been there, I am not sure. I plan to monitor it daily and watch for signs of change. Any assistance/feedback/suggestions would be greatly appreciated.

      1. Thank you very much, I greatly appreciate your feedback and reassurance! I do keep a very close eye on it now that I know it is there. Last evening, I was feeling it and moving his fur to see if I can see anything on the skin itself and it was not visible at all. I even gently pinched the skin to lift it up somewhat as a tent and the lump did not come with the skin. It almost feels as though it’s attached to his muscle itself. Would it be possible to be some form of trauma that could have occurred from bumping into something, or playing with the other dogs? Or does the location and description sound more so as a fatty tissue/cyst?

        I will monitor and take him to the vet if anything changes.

        Thank you for also sharing the article about the grain free diet he is on. I had no idea about the concerns of a grain free diet. I will now be switching my dogs food over to a grain salmon diet, as I believe the salmon aspect of it has been very good for all 4 of my rescues coats.

  2. Hi my dog has a large swollen bump like mass on her left side basically on the her butt bone just above the swirls. It doesn’t seem to hurt her even to the touch. It moves under the skin and hair it’s simi soft but kinda firm very concerned for my Great Dane she’s only 11 months if u can help at all please

    1. Hi Gracie. This definitely needs to be seen by a vet, as it’s very unlikely to be a lipoma. A simple fine needle aspiration should give the answer.

  3. Hello, my female pug ( has been spayed) has a big lump on her abdomen. It is around 2 inches in diameter. When I press on it or move it she yelps. It is soft also.

    1. Hi Kylee. If she was just done, it’s probably a seroma of only minor concern but it could also be a hernia if the internal stitches have come apart. Keep her quiet and visit a vet as soon as you can.

  4. Hey, I have a french bulldog who is 4 in June, he hasn’t been nurtured. I have recently found/seen a lump under his bum, It does resemble and in the same location of the picture you posted in relation to the hernia however should I be worried?

    Thank you in advance! 🙂

  5. Hello! I have a male basset, in tact, very healthy and very energetic. In the past week or so I noticed a lump on his right front leg, about the size of a pea. Next to it there was another very small bump. In the week that has passed, it has grown twice in size and he now has about 12 small bumps smaller then the size of a pe around his neck and other leg. Waiting to go to the vet. I am concerned about how sudden this has happened. Have you seen something like this before?

  6. Hi, I have a seven year old male golden retriever. I just noticed a pretty good size lump under his skin in his lower left abdomen. It appears soft and moves a little, doesn’t seem to bother him. It’s worrisome due to the size and location. The lump is bigger than a grape but smaller than a golf ball. Should I watch it for a while or get him into the vet immediately? I appreciate your time & help, thank you!

  7. Hi we have a dog that has developed a red hot firm but maybe a little squishy lump under her left armpit and up her left side. It’s about 8 inches by 4 inches and possibly growing. She also developed edema this morning on her left side and left leg. She’s had a FNA and a round of antibiotics. Cancer cells were not found but we have no answers right now. She’s currently having an incisional biopsy. They are switching her antibiotics and putting her on steroids. Any suggestions has to what this might be? There is also some skin puckering. Snake bite, Spider etc

    1. Hi Amy. Without knowing her age and neutering status it’s very hard to answer that question. Spider bite would be rare in that location. The only lump (other than infection) I know that is noticeably hot is inflammatory carcinoma which is a rare form of mammary tumour. However, a biopsy is always best.

  8. Hi, my German Shepherd Mia, has a pea shaped/sized lump under the skin next to one of her teats. She is spayed, she’s also 8 yrs old.
    She was spayed about two years ago. She did have one litter of puppies when she was 1 yr old.
    This lump is very recent as i do check her frequently. What could this be? With the current situation money is very tight and i’m afraid to take her to the vet with everything thats going on.

    1. Hi Mayrelen. This is almost certainly a mammary tumour, which occur in most dogs spayed at a late age like Mia. It will need to be removed, and the sooner the better.

  9. I have a 3 year old female English pointer that has palpable lump on her right ribcage about the middle of the body. Lump is under the skin, does not have color. It’s soft in some area and harder in other. The confusing part that it keeps changing size, it’s been there for about 2 months now. It started small then swallows larger from activity, but gets smaller again overnight. Overall it’s grown over 2 months, and now is about the size 4″ * 2″ & 2/3″ deep. But with pattern of getting smaller some days, and larger other. We took 14 day of antibiotics, it’s gotten smaller during the course, but did not disappeared and still acts the same. Help please, can’t find info online on size changing symptom.

  10. I am asking for some advice as found a lump on dogs right side upper chest nearer armpit. The good thing I do believe is that its a lypoma as being a bodybuilder Ive got 3 lumps that feel exactly the same as my dogs. Its easy to move around has no colour its just under the skin but not too deep. Ive measured it and will keep an eye on it over next few weeks to see if growth increases. Let me know if im doing correct things as just lost his mum 5wks ago due to her taking seviere cluster of seizures so im heart broken. Hard as losing a family member but she was a family member. Thankyou for reading this.

  11. My baby girl who is 12 and a JRT cross now has two x inch diameter soft lumps on her belly. Took her to the vet on finding the first one and he said not to worry, without doing a biopsy. Now the second one’s come up. Do I take his word or do I insist on a biopsy?

    1. Hi Sarah. He’s probably right, but without a fine needle aspiration (taking about 1 minute per lump) it’s only an educated guess.

  12. I have an a great Italian greyhound she’s 16 miniature she had I have found several black movable lumps under her skin neck down by her inside one of her thighs on her leg inside live a leg what could this be she hasn’t been eating well and sleeps constantly her eyes are really red rammed in sheet her hair on her legs is he’s gone

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