Fatty Tumors in Dogs

There is a lady in our neighborhood who walks a little pug that has the largest fatty tumor that I have ever seen. It hangs underneath the dog’s belly and nearly touches the ground when he walks. I swear the tumor is at least half the size of the dog itself. Have you ever seen a dog with a large fatty tumor? It is kind of horrifying when you first see it. I feel so bad for this little dog. He is pitiful. He is a very old pug, which is probably why the owner has chosen not to have the tumor removed.

It seems like every dog I ever owned developed a fatty tumor as they got older. Rex has two smaller ones – one under his right front leg and one on his chest. Fortunately, they are completely benign. I don’t think Rex even has a clue that they are there, and for that I am thankful. At this point, both fatty tumors are fairly small, but they are growing slowly. I hate them. They spoil what is otherwise his perfect little canine physique.

What is a fatty tumor?

I’ve always called them “fatty tumors”, but some people refer to them as “fatty cysts”. They are most commonly referred to in the veterinarian community as lipomas, lipoma tumors, or adipose(meaning: storage of fat) tumors . Sounds scary, doesn’t it? Anything with the word “tumor” in it is frightening. Nine times out of ten (that’s not a statistic, just a figure of speech), lipomas are nothing to be afraid of.

“Fatty tumors” are probably the more descriptive word for these tumors because that is exactly what they are – a mass of fat cells. The medical community, though, uses the word “lipo”, which also means “fat”. It is used in many medical terms – liposuction, liposomes, lipoproteins, etc.. Lipomas are soft, “mushy” little sacs of fat tissue just below the skin’s surface. They are usually round or round-ish. Lipomas are mostly located on a dog’s torso or legs, but they can be anywhere. If a dog gets one tumor, they are likely to get another and there is no reason for that, other than they just grow in multiples. Fortunately, lipomas do not spread but they do grow in size.

Fatty tumors in dogs can be very large. I read an article yesterday of a homeless Golden Retriever who had a 46-pound lipoma. That poor dog. You don’t see them that large very often, thank goodness, but they can be large enough to cause your dog some discomfort. Fortunately, they don’t hurt. They are only painful if their location causes the pain, i.e., if they are pressing on a nerve, or if they are in an area that somehow hampers the dog’s movement. This poor golden retriever could hardly walk because of the sheer weight of the lipoma.

Should I be concerned if my dog has a fatty tumor?

Lipoma tumors are fairly common, especially in middle-aged and senior dogs. I not only have seen them in my own pets but have also seen them in many of our older guests at Holiday Barn Pet Resorts. “Embrace Pet insurance” estimates that About 16% of dogs are affected with lipomas. That does not sound like much (and I was kind of shocked by that statistic) but considering there are close to 77,000,000 dogs in the US, that means that over 12 million of them develop lipomas. That’s pretty significant when you look at it that way.

It seems there are certain dog breeds that are more likely to develop lipomas, some of which are labs, dachshunds, Weimaraner’s, Doberman pinschers. If you will notice, these are short hair dogs… I can’t help but wonder if lipomas are also predisposed in many dogs with long hair, but we are just not likely to see them in all that hair. It has also been reported that they affect female dogs more than males. Overweight dogs and older dogs are usually the ones to develop fatty tumors, but they have been known to develop in younger dogs – not often, but it does happen.

Can a fatty tumor be dangerous?

Lipomas are usually not harmful but should not be taken for granted. Ever-so-often my vet performs a fine-needle aspiration to collect cells from Rex’s lipomas. She then looks at it under a microscope or sends it to be looked at by a pathologist to be sure cancer cells are not present or have not developed over time. It is very rare, but sometimes the fat cells within the lipoma can evolve into a liposarcoma.

Liposarcomas are the malignant form of fatty tumors. It’s not that the lipoma “turns into” a liposarcoma, but rather the fat cells within the lipoma form the malignant tumor. I know, that’s hard to understand but all we really need to remember is that it– thankfully – is rare. Your veterinarian will be able to determine if a liposarcoma is present when performing a fine needle aspiration. Dogs have a good chance of recovering from the removal of liposarcoma if it is caught early on. Radiation is sometimes recommended after removal to help prevent a recurrence.

Another type of dangerous fatty tumor is an infiltrative lipoma. It is when a lipoma penetrates the muscles. It can also invade the nerves, bones, tendons, blood vessels, joints, etc.. It’s hard to tell a “normal” fatty lipoma from an infiltrative lipoma. Where the fatty tumor stops and the infiltrative lipoma begins is difficult to determine. Because of this, it is nearly impossible to remove completely, and if attempted, there is a good probability that it will return.

I have to mention… please don’t confuse a “lipoma” with “lymphoma”. Lymphoma is cancer of the lymph nodes and is in no way related to lipomas, with exception to a similar pronunciation.

What causes fatty tumors in dogs?

There appears to be no conclusive research on why dogs develop lipomas, but there are some interesting suggestions.

One source surmises that a lipoma is a buildup of toxins that the dog’s body is unable to get rid of. A fatty tumor is formed when the body tries to rid itself of unwanted toxins and yucky stuff through the body’s largest organ, the skin. This same source says that lipomas are usually a sign of kidney or liver dysfunction. This makes sense to me, however, I have only seen this mentioned elsewhere only one other time in my research. Also, I have never received that kind of feedback from my veterinarian, nor from any of the veterinarians I have visited with my dogs that have had lipomas over the years.

That said, lipomas are found in healthy and unhealthy dogs. The exact cause may not be known, but since it is prevalent in certain breeds (as mentioned above), it makes sense that there is a genetic component. The truth is, very few tumors have a single cause. There is usually a blend of several factors… genetic, environmental, lifestyle, etc. Since lipomas occur more in female than in male dogs, maybe there is a hormonal reason for them as well.

Should I have my dog’s lipomas removed?

Most veterinarians advise against the removal of lipomas unless they are causing a problem for the dog. If there are no problems, the surgery would be purely cosmetic… And our dogs really don’t care what it looks like.

If we decide we want the unsightly lump removed for cosmetic reasons, we need to understand that there is a chance the lipoma will reoccur. Also, removal sometimes carries a risk of post-surgical complications (i.e., swelling, infection near the incision site), but that is a possibility any time an incision is made. Another consideration for senior dogs is that they could have a whole lot of stitches to have to deal with, and a long recovery time because of their age. I guess we need to ask ourselves, is the pain and discomfort we would be putting our pet through really all that necessary?

Liposuction is another method sometimes used to remove lipomas. Liposuction would be a less invasive option to surgery. It requires a small incision with less anesthesia. Recovery time is quicker too. Unfortunately, regrowth rate is higher with liposuction.

Other methods have been tested… laser therapy, steroid injections, acupuncture, but none of these methods have been widely supported by the veterinarian community.

Checking your dog for lumps

A dog’s hair sometimes makes lumps difficult to see. The only way you can really check your dog for lumps is to run your hands over their entire body – and this includes all over the muzzle, between the legs, inside the ears, down the tail, around the paw pads. I would even suggest checking inside the mouth. Do this at least once a month. If you feel anything out-of-the-ordinary, have it checked by your veterinarian. There is a better chance of successful treatment or removal of any tumor while they are still small, so you want to catch them as soon as possible.

One mistake sometimes made by people like me who have had several senior dogs with lipomas, is to assume that a “squishy mass” under the skin is just a benign lipoma. Mast cell tumors and soft tissue sarcomas can feel just like a lipoma under the skin. We should always report any lumps to our veterinarian for examination.

How can I prevent lipomas in my dog?

I say this often for so many scenarios: All we can do is the best we can do… Particularly when the cause of lipomas is still uncertain, right?

Feed your dog highly nutritious, minimally processed food.
Help them to maintain a healthy weight.
If possible, give them fresh filtered water to drink.
Make sure they get good exercise.
Try to limit their exposure to toxins (i.e., pesticides, cleaning supplies in the home).

Annual medical checkups are also a must, and as your dog ages, take them for a checkup semiannually. These are always good practices for optimal health in your pet.

A side note…

Henry, the stray golden retriever with the 46-pound lipoma? The authorities found his owner. She had abandoned Henry while he was struggling with the tumor, and was charged with life-endangering animal neglect, failure to care for an animal, and animal abandonment. She was sentenced to 56 hours of community service, fined $7,346 in reimbursement for Henry’s care, ordered to attend a 16-week animal neglect prevention program, and prohibited from owning, caring for or living with an animal. Henry’s tumor was successfully removed. He went from 124 pounds to a svelte 78 pounds and lived-out the rest of his years in comfort.

Fatty Tumors in Dogs