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What to Know About Fatty Tumors (Lipomas) in Dogs

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Layne is an animal lover and grew up in a household full of rescued critters. She is a registered veterinary technician.

All About Lipomas in Dogs

All About Lipomas in Dogs

What to Do If You Find a Fatty Lump on Your Dog

Millions of dogs in the United States alone see the vet for lipomas every year—a common type of fatty tumor that appears under the skin. As dogs age, it is not uncommon for them to develop mysterious lumps and bumps. Some breeds, too, are prone to developing skin anomalies.

Our English Spaniel developed a fairly large fatty lump on her flank at around six years of age, and now she has nearly five smaller ones all throughout her torso. While in most cases fatty bumps or lipomas are benign and only require surgical removal, if they restrict mobility or similar, you do need to watch them; your vet should perform a fine needle aspirate on each lump to make sure that they are non-cancerous.

What Is a Lipoma?

A lipoma is a common term that is used to refer to a benign fatty tumor that often appears on adult or senior dogs. Some lipomas stay the same size for years and others may grow; in addition, your dog might first develop one and then develop several others in months or years. They grow nearly everywhere, but they generally present right below the skin. Sometimes they grow in muscle tissue and muscle layers—such types are called infiltrative lipomas. Occasionally, fatty tumors may cause discomfort for your pet and might need to be surgically removed.

Learn about what treatment options are available for fatty tumors in dogs.

Learn about what treatment options are available for fatty tumors in dogs.

What Does a Fatty Tumor Feel Like on a Dog?

Lipomas (fatty tumors) generally feel rounded, small, and sphere-shaped. They can also be hemispherical and have a generally smooth texture under your dog's skin. Some tend to be firmer and adhered to tissue, but most are quite movable and generally bouncy or soft to the touch. You should be able to manipulate the tumor on your dog without pain. It should not be oozing, bleeding, or scabbed. It is not uncommon for lipomas to range from small in size (walnut-sized or smaller) to the size of a grapefruit on larger breeds (in which case, your vet should have already discussed surgical removal). Larger lipomas can weigh several pounds and may be extremely uncomfortable even on larger breeds.

Are Fatty Tumors in Dogs Dangerous or Cancerous?

Lipomas are not cancerous. If your dog is diagnosed with a true lipoma, meaning, it is definitely fat cells only, then you can rest assured that the growth is not cancerous and instead benign (rather than malignant). The growth will not metastasize. However, it is important to know that some dogs will develop multiple lipomas in their lifetime, and although they are benign, they can sometimes cause discomfort or impede basic function and might require surgical intervention (such as in the armpit or legs).

Some lipomas show up and stay the same size for your dog's lifetime and others grow and increase in size. Other times, several small lumps may show up rapidly and change or stay the same size and shape. It's always important to watch them regardless and to point out any new growths to your vet upon each check up.

Liposarcomas (Cancerous Fatty Tumors) vs. Lipomas

Liposarcomas are malignant and are often recurring. They are categorized in the group of soft tissue sarcomas. They require aggressive treatment. Although extremely uncommon, they do metastasize and spread to other parts of the body. They can be felt as semi-firm lumps under the skin or in the muscle. They are not painful. In such cases, tissue biopsies using local anesthetic are recommended to determine the grade of the tumor via sample. These tumors are considered invasive to surrounding tissue and can metastasize to other organs (though rare).

If your dog is indeed diagnosed with a liposarcoma(s), they may be required to undergo radiation therapy or chemotherapy in addition to surgical removal. A pathologist will evaluate the tumor(s) post-surgery to determine the type, grade, and margins (e.g. was all of it removed?). Your vet will know what to do, but first, the growth needs to be evaluated—do not wait.

What Causes Lipomas to Form?

It's not well-known why dogs tend to develop lipomas besides age. Oftentimes they are hereditary, although several breeds are prone to them. Sometimes they can be caused by physical trauma. Below, are some common causes of lipomas.

Poor Diet

It is thought that carbohydrates, preservatives, and toxins found in processed dog food can contribute to fatty tumors.

Chemicals

Tap water also contains chlorine, which can upset thyroid levels and disrupt the endocrine system. The endocrine system and immune system are responsible for eliminating and excreting unwanted material in the body via the skin, however, fatty tumors may form in the body's efforts of eliminating such material.

Environmental

Pesticides and herbicides in your dog's environment can contributor to the development of tumors. Avoid using such products in your yard or areas around the house. You can also bathe your dog or wash off their feet if they encounter such chemicals so that they don't accidentally ingest them or absorb them through their paw pads.

Breeds That Are Prone to Lipomas

All dogs are susceptible to developing lipomas, especially those that are middle-aged and older. However, some breeds are prone to them. These breeds include: Labrador retrievers, Weimaraners, Doberman Pinschers, Boxers, and spaniel breeds.

Senior dogs are prone to developing multiple lipomas.

Senior dogs are prone to developing multiple lipomas.

How Are They Diagnosed?

Lipomas are often diagnosed with what's called a fine needle aspiration (or FNA). It's a fairly common procedure, painless, and your dog does not need to be put under for it so long as the tumors are fairly superficial. Your vet will have an assistant restrain your pet comfortably. They will then insert a small needle into the fatty tumor and suction out a small sample of cells from the lump. They will then blow the tumors from the syringe onto a microscopic slide for examination.

In most cases, fat or adipose cells can be identified on the slide and the diagnosis made. In rare instances, an FNA might not be enough and your dog may need a biopsy. A biopsy generally involves taking a small sample of the tumor for a pathologist or lab to review. Termed histopathology, a biopsy will allow for a firm diagnosis of the types of cells present in the tumor.

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Should Fatty Tumors Be Removed From Dogs?

Once your vet has performed a fine needle aspirate (FNA) and the tumor growth has been diagnosed as a lipoma, you will likely discuss with your vet whether or not it has to be removed. If it is impeding your dog's mobility or uncomfortable for them, it will be removed surgically and under anesthesia. In some cases, your veterinarian might require that your dog undergoes a CT or MRI to determine how deep or invasive the tumor is.

If your dog is older, it's possible that surgery might be avoided entirely. Sometimes the surgery is actually riskier (due to tumor location, pre-existing health conditions, age, and other factors that make your dog a high-risk anesthesia patient).

Lipomas are common in older dogs.

Lipomas are common in older dogs.

How Can I Shrink Them?

Although surgery is often the most common approach for getting rid of a lipoma, you can make some changes in your dog's daily health and wellness routine to better their chances for fatty tumor reduction.

Nutrition: For one, make sure your dog is on quality food (preservative, chemical, dye, and additive-free foods). In addition, avoid offering your dog tap water (which is laden with chemicals). You will want to make sure you know what you are putting into your dog's body. Offer them the healthiest options possible.

Exercise: Make sure your dog is receiving the proper amount of exercise recommended for their life stage. Exercise is an important part of overall health for your dog, especially if they are housebound.

Weight loss: Make sure your dog is also at a healthy weight. Excess fat and weight gain essentially feed the fatty tumors. Talk to your vet about cutting down on your dog's weight (what their ideal weight range is). Stop feeding scraps and garbage snacks, and offer some healthy alternative treats when needed.

Avoid chemicals: As always, avoid using herbicides, pesticides, and other endocrine disrupters in your house or on your lawn. Some chemicals that are used for cleaning indoors can be problematic too and might be considered endocrine disrupters. Keep your living space healthy and avoid exposing your animals to troubling ingredients.

Mental wellness: Immunity and bodily health are closely tied to overall wellness. If your dog is stressed, depressed, or unhappy, this can affect them on a physical level as well. Take care of them holistically and offer them everything and more. Their health will benefit!

Sources

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2021 Laynie H

Comments

Laynie H (author) from Bend, Oregon on January 17, 2021:

Hi Liz, I agree to always get it checked out too just to be safe. It's a relief to find that they are simply fatty (benign) tumors. Regardless, having a good resource to learn about them is pretty critical. I hope this article can help other owners who have lots of questions.

Laynie H (author) from Bend, Oregon on January 17, 2021:

Hi Lora, thanks for sharing your experience with lipomas. I definitely get nervous with any kind of lump and it's important that we check them out. I am sad to hear about your foster dog having cancer. That is my greatest fear. I'm glad you find the article helpful.

Laynie H (author) from Bend, Oregon on January 12, 2021:

Hi Peggy, thanks for reading. Glad to hear your dog's lipomas weren't problematic. Our dog just developed several more recently, so I thought I'd write a bit about it to help other owners feel some relief. We had them all checked and they were just fatty lumps.

Peggy Woods from Houston, Texas on January 11, 2021:

One of our dogs had some lipomas, but they were not cancerous or impeded her in any way, so they were not removed. Thanks for writing this informative article.

Lora Hollings on January 10, 2021:

This is an excellent article on benign fatty tumors in dogs versus cancerous tumors in dogs, Lane. For the dog's well being as well as the owner's peace of mind, it is important to have any lumps checked out. Our Westie mix has a number of lumps that are just lipomas. But we had fostered a dog which had a large tumor on his head which sadly turned out to be malignant. What the vet thought was a superficial tumor was actually attached to the bone and he was ultimately diagnosed with cancer of the sinuses. There was nothing that could be done as it had already metastasized. It was very sad because we loved this sweet boy so much. You also give some excellent suggestions on reducing the size of lipomas as well. We try to do all of these to keep our dogs healthy and happy! Thanks for sharing this important information for all dog owners.

Liz Westwood from UK on January 10, 2021:

This is a helpful and interesting article. Often when a lump appears we are prone to think the worst. This helps yo set the record straight and reassure dog owners that not all lumps are cancerous. It sounds like it is best to get them checked out though.

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