Lipomas in Dogs

Lipomas in Dogs, Also Known as “Fatty Tumors”

Canine lipomas are benign (non-cancerous) masses made of adipose (fat) cells. Your veterinarian might call a lipoma a “fatty tumor.” Lipomas in dogs typically don’t metastasize (spread) to other parts of the body.²

Because fat is found in many parts of your dog’s body, lipomas can occur anywhere, including deep inside. However, most lipomas noticed by dog owners occur on the chest, abdomen, and legs, right under the skin where a layer of fat is normally present.

You may also hear the term “infiltrative lipoma,” which is what some veterinarians call lipomas that grow in-between muscle layers.

Malignant Lipomas (Liposarcomas)

The malignant form of lipoma is called liposarcoma. These types of tumors in dogs are very rare. In general, they will be treated much more aggressively and monitored much more closely than benign lipomas. The following sections will touch on malignant liposarcomas in dogs when applicable.

What Dogs Are Prone to Lipomas?

Lipomas are more likely to occur in overweight, older dogs.

What Do Lipomas Look Like on Dogs?

Lipomas in dogs typically start as a small, single lump under the skin. The fur and skin over the mass are typically normal in appearance.

Lipomas in dogs can vary in texture. The mass itself is usually soft, squishy, and can be gently manipulated. Your dog’s lipoma may be circular, oblong, or irregular and bumpy.

Some may be firmer due to their attachment to underlying tissues.²

It’s also possible – even likely — that your dog can have multiple lipomas, especially as he or she ages. Keep in mind that each of these lipomas is an individual and may develop differently. While some may grow rapidly, others may take years before they grow large enough to be concerning.

Because they’re benign, lipomas are not considered cancerous and do not metastasize to other areas of the body. However, lipomas themselves can grow over time, becoming very large.

Lipomas can become problematic if they:

• Affect or block the blood supply
• Pinch nerves or otherwise cause pain
• Prevent normal movement

These problems are more likely to occur if a lipoma is fast-growing or grows in an inconvenient location on the body such as the armpits, scrotal area, or head and neck area.

Some lipomas are unnoticeable and stay the same size for many years. Many do not cause any symptoms, can be readily diagnosed, and do not require treatment.

However, if you notice your dog’s lipoma is developing an abnormal appearance, has a change in growth pattern or rate, or is causing discomfort, your veterinarian may recommend surgical removal. Often surgical removal of lipomas is done while the dog is under anesthesia for some other reason, as it is rarely an emergency.

Stats and Facts

Because lipomas are not generally dangerous tumors and don’t limit the lifespan of dogs in general, there isn’t a lot of money or effort spent studying them. However, insurance records can tell us a lot about conditions being treated by veterinarians. Embrace Pet Insurance claims that the percentage of dogs affected by lipomas is about 16%.² Middle-aged and older obese, female dogs are most pre-disposed to developing them.²

Causes of Lipomas in Dogs

There is no specific known cause for lipomas in dogs. Most veterinarians believe that tumors in dogs are caused by a combination of different environmental, hereditary, and genetic factors. Since lipomas appear to occur in some breeds more than others, it is likely that at least some genetic link is responsible for lipomas in dogs.²

Case studies show anecdotal support for an environmental link to lipoma development. One published paper outlined the growth of 72 lipoma tumors on a dog who was living in a family home that was exposed to mold and mycotoxins.⁴

Risk Factors

Although any breed of dog can grow lipomas, they appear to be more common in some breeds:²

• Doberman Pinschers
• Labrador Retrievers
• Cocker Spaniels
• Weimaraner
• Schnauzers
• German Pointers
• Beagles
• Golden Retrievers

Symptoms of Lipomas in Dogs

Many lipomas are noticed at home first. Some are found by the family veterinarian during a routine wellness exam.

You may initially feel or see a small lump under your dog’s skin. If a lipoma has grown large without you noticing at first, you may see some change in your dog’s normal appearance or routine. For example, you may notice your dog’s walk has changed if a lipoma has grown in the armpit area. You may notice your dog licking or chewing a new mass under his skin. Although lipomas are not typically painful, your dog may show signs of discomfort if he has an injured lipoma.

If you discover a new or changing mass on your dog, you should contact your veterinarian right away.

Diagnosis of Lipomas in Dogs

While most lipomas in dogs have a distinct look and feel, there are other tumors that can resemble lipomas. A quick way to check if the mass is truly a lipoma is for your veterinarian to examine a cytology obtained by fine-needle aspirate (FNA).

Though this method is often very reassuring, it is critical for owners to understand that this method is not perfect. Cytology by fine-needle aspirate (FNA) only examines a small number of cells from the suspected lipoma. In other words, in some rare cases, there are other tumor cells hiding within or behind the apparent fatty lipoma cells.²

Lipomas are often easy to identify with an ultrasound. Common features that can be seen include an oval or irregular shape, a defined capsule, and a consistent thin striped echo pattern throughout the mass.⁶ Additionally, the ultrasound can help your veterinarian get a more accurate cytology sample by guiding your veterinarian to the center of the apparent lipoma, to collect any non-fatty tumor cells that may be present.⁶

A biopsy (removal of a piece of the tumor) of the tumor is required for a definitive diagnosis.⁵ In some rare cases, advanced imaging, such as a CT scan, may also be recommended.

It is critical to do at least an FNA and cytology of all lumps, even if they feel like a fatty tumor – they may well be a simple lipoma, but more sinister cancers can look and feel similar.

Prognosis and Staging

Lipomas in dogs are almost always non-cancerous, and do not spread to other parts of the body or involve local lymph nodes.² Because of this, most veterinarians do not stage lipoma tumors in dogs.

The prognosis for a normal length and quality of life for a dog with one or more lipomas is quite good. Lipomas are benign tumors that respond well to surgical treatment and should not be life-limiting for dogs.

Treatment

Once a diagnosis of lipoma is confirmed, the slow-growing nature of lipomas may simply mean that you only have to monitor your dog’s lipomas for changes in appearance, texture, and size.² Taking pictures with your phone along with measuring and recording the size, shape, and firmness of the lump at least every six months will help you note any changes.³

If any of the following are seen, report it to your veterinarian:

• Growing very quickly
• Becoming more firm
• Becoming lumpy
• Developing discharge
• Causing your dog pain
• Interfering with your dog’s movement
• Are otherwise looking or feeling different (not just bigger)

Because the majority of lipomas don’t cause problems, some veterinarians recommend simply monitoring. Some lipomas may stay the same size for years, while others may grow big enough to affect mobility. For lipomas that do cause discomfort or other problems for your dog, the best treatment is surgical removal.

A diet plan is often needed to keep your dog at a healthy weight.³ As lipomas are made of fat cells, maintaining a healthy body condition for your dog helps to control lipoma growth and prevent future lipomas from developing.³ Your dog’s lipoma may even shrink as she drops some pounds.

Surgery

Surgery under general anesthesia is considered curative for lipomas in dogs.⁶ Most lipomas are in a soft capsule and can be surgically removed entirely. Once removed, the recurrence rate is relatively low.

Although lipomas are not cancerous and will not metastasize, large lipomas — or lipomas in the wrong location — can definitely cause issues. In some cases, it can help to surgically remove the lipoma while it is still small. This surgery will likely be less invasive, less painful, and heal quickly. Surgery to remove larger lipomas is more difficult for your veterinarian to perform and more difficult for your pet to recover.

Since lipomas are benign, some veterinarians will recommend waiting to remove the lipoma until your dog is going under anesthesia for some other reason. Others will recommend removing the lipoma before it grows to a troublesome size. Be sure to follow your veterinarian’s recommendations.

Lipomas are relatively less expensive to treat than other “lumps and bumps” because they are not cancerous.² Surgery may cost you between $200 to $500 per mass to be removed.² This price can of course increase upwards of $1,000 based on the size of the lipoma, its location, and whether or not it’s a liposarcoma (the malignant form of lipomas).²

The risks of surgically removing a lipoma are the same as any surgery:⁶

• delayed wound healing
• infection
• seroma (collection of fluid at the surgical incision site)
• hematoma (bruising)
• nerve damage
• standard anesthetic risks

Some infiltrative (growing into the nearby muscle) lipomas will grow back after being surgically removed. Your veterinarian may recommend surgical removal again, with radiation therapy as a follow-up to help ensure it does not grow back again.¹

For a case of liposarcoma (the rare malignant version of lipoma) multiple surgeries may be needed. Liposarcoma tumors are cancerous and have a high rate of recurrence.¹ Though uncommon, liposarcoma may also metastasize.¹ Your veterinary oncologist will likely suggest a much more aggressive treatment plan if your dog’s suspected lipoma is actually a liposarcoma.

Liposuction

Liposuction is a relatively newer technique being used to remove larger lipomas. Liposuction is minimally invasive and can be helpful if other treatment options are not an option or have failed.^2,6 Unfortunately, with liposuction, there is a high likelihood the lipoma will grow back.

Chemotherapy

Chemotherapy drugs are not a standard therapy for lipomas in dogs.

However, one small study showed encouraging results from injecting a steroid called triamcinolone directly into the lipoma. This caused regression in smaller tumors without the need for anesthesia and surgery.⁷ It may be a treatment option for the future.

Radiation

Radiation may be used as a follow-up to surgery to stop the lipoma from growing back. Radiation can be beneficial for infiltrative lipomas, areas at high risk for recurrence, and surgical mass removal with incomplete margins.

Radiation does come with its own risks and costs, so it is not a common recommendation to irradiate benign lipomas. Radiation is more common in the treatment of liposarcomas that have already been surgically removed once before.

Immunotherapy

As lipomas are benign and often cured with surgery, there is no known immunotherapy treatment.

Vaccine

As lipomas are benign and often cured with surgery, there is no known vaccine treatment.

Diet

Providing a healthy, fresh, preservative-free diet helps to maintain overall health.

Overweight dogs are more likely to develop lipomas. Weight loss and a balanced, nutritionally appropriate diet will help to shrink the size of your dog’s lipoma and minimize the risk of new ones developing in the future.⁴

Certain nutrients have received anecdotal support for their ability to prevent lipomas, including vitamin C, vitamin B-12, chromium, and L-carnitine. These are occasionally recommended as nutritional supplements in addition to a balanced diet. More scientific study is needed to determine their efficacy.

Fish oil, a known source of omega-3 fatty acids, has proven benefits for dogs. It may be helpful in the reduction of inflammation and obesity, and in promoting the health of your dog’s joints, skin, and coat.⁸

Supplements

You should always talk to your veterinarian before adding any supplement to your dog’s regular regimen. Most nutraceuticals (natural compounds thought to have health benefits) lack scientifically rigorous studies that show their efficacy.

There is anecdotal evidence for certain natural remedies preventing, slowing the growth of, or shrinking lipomas. These nutraceuticals contain ingredients that are bioactive, along with phytonutrients that have antioxidant and anti-inflammatory properties.⁸

Herbs and plants that may be helpful in treating lipomas include:⁸

• Turmeric (curcumin)
• Chamomile and dandelion root
• Burdock root
• Chickweed
• Violet
• Milk thistle
• Olive extract
• Grape seed extract
• Thuja tree
• Alfalfa
• Apple cider vinegar
• Goldenseal
• Self-heal

Your veterinarian will be able to refer you to a holistic veterinarian, or help you figure out dosing and legitimate sources of nutraceuticals. This is a key reason why you should always consult your veterinarian before adding a supplement. You want to make sure that it is a good fit for your dog and that it won’t interfere with any of her medications or treatments. Also only add one supplement at a time, so that if your dog reacts to it poorly, you will know exactly which thing they didn’t tolerate.

In most cases it is better to choose a few supplements that target your dog’s primary needs, rather than many. This will also help to keep costs down.

Integrative Therapies

Alternative therapies are a part of integrative veterinary medicine. These methods are typically outside the norm of generally prescribed therapies, but nonetheless may have benefits for your dog.

For example, therapeutic laser therapy uses red and near-infrared light to stimulate damaged cells to regenerate. A small 2009 study achieved complete or near-complete dissolution of lipomas in 100% of their patients who received laser therapy.⁷ However, in general it is still not recommended to laser any tumors, so be sure to follow your veterinarian’s recommendations.

The End

Lipomas are benign tumors in dogs, with no metastatic risk. They should not shorten any dog’s lifespan.

The life quality for a dog with many lipomas may need to be assessed. Factors to assess include:

• your dog’s age
• the size of your dog’s masses
• number of masses
• location of masses
• interference with normal activities
• whether the mass (or masses) is ulcerated and at risk for infection.

Prevention Strategies

The cause of lipomas in dogs is not known, though a combination of heredity and environment is suspected. Prevention may not be entirely possible.

Lipomas occur more often in dogs that are overweight and who have more fatty tissue. Keeping your dog at a healthy weight may be one way to help prevent lipomas, or possibly keep them from growing.

Supplements that contain specific compounds and vitamins, such as fish oil, vitamin C, vitamin B-12, chromium, and L-carnitine may help prevent lipomas or shrink existing ones.⁸ These supplements can also have additional benefits, such as those that support joint health.