The exact cause of fatty tumors in dogs is unknown, but the strongest risk factors are excess body weight, advancing age, genetics, and neutered status. These benign growths, called lipomas, form when fat cells multiply and cluster together beneath the skin, creating soft, rubbery lumps that are almost always harmless. About 2% of all dogs develop at least one lipoma during their lifetime, and many dogs develop several.
Obesity Is the Strongest Modifiable Risk Factor
Of all the factors linked to lipomas, body weight has the clearest statistical relationship. Dogs with a body condition score of 7 or higher on a 9-point scale (meaning noticeably overweight) have roughly five times the odds of developing a lipoma compared to dogs at a healthy weight. Even dogs that are only slightly above average for their breed and sex carry nearly double the risk.
This makes sense biologically. Lipomas are masses of adipose (fat) tissue enclosed in a thin capsule. A dog carrying more fat tissue has more raw material available for these clusters to form. While losing weight won’t make an existing lipoma disappear, keeping your dog lean is the single most effective thing you can do to reduce the chance of new ones appearing.
Age and Hormonal Changes
Lipomas are overwhelmingly a condition of middle-aged and older dogs. They rarely appear in young animals, and their prevalence climbs steadily after about age six. This pattern suggests that cumulative changes in metabolism and hormone regulation play a role, though no one has pinpointed the exact mechanism.
Neutered dogs of both sexes are more likely to develop lipomas than intact dogs. Spaying or neutering alters the hormonal environment permanently, which can shift how the body stores and regulates fat. This doesn’t mean neutering is a bad decision (the health benefits typically outweigh this particular risk), but it’s part of the picture.
Breeds With Higher Risk
Certain breeds develop lipomas far more often than others, pointing to a genetic component. Labrador Retrievers are the breed most commonly associated with fatty tumors, but a large UK veterinary study also identified Weimaraners, Dobermann Pinschers, and German Pointers as breeds with elevated risk. Larger breeds in general seem more prone than small breeds, though lipomas can appear in any dog.
If your dog belongs to one of these breeds, finding a soft lump under the skin at some point in their life is common enough that most veterinarians consider it almost expected. That said, breed predisposition is not destiny. Plenty of Labs never develop a single lipoma, and plenty of mixed-breed dogs do.
What a Lipoma Feels Like
Lipomas have a fairly characteristic texture. They feel rubbery and relatively soft, sit just beneath the skin, and move freely when you press on them. They most commonly appear on the torso and limbs. They grow slowly, sometimes taking months or years to reach a noticeable size, and they don’t cause pain unless they grow large enough to press on surrounding structures.
Most dogs that develop one lipoma will eventually develop others. Finding a new lump every year or two is a normal pattern for predisposed dogs, not a sign that something is getting worse.
When a Lump Needs Testing
Not every lump under the skin is a lipoma. Mast cell tumors, a potentially serious type of skin cancer, can sometimes feel similar to the touch. The standard first step is a fine needle aspirate: your vet inserts a small needle into the lump, draws out a few cells, and examines them under a microscope. Fat droplets from a lipoma look distinctly different from mast cell tumor cells, so this quick in-office test can usually provide a clear answer.
The one limitation is that all three forms of lipoma (simple, infiltrative, and malignant) can look identical on a needle aspirate. Simple lipomas are by far the most common and stay neatly contained inside their capsule. Infiltrative lipomas grow into surrounding muscle and connective tissue, making them harder to remove. Malignant lipomas (liposarcomas) are rare but can spread. If there’s any question about which type your dog has, a tissue biopsy provides a definitive answer.
Treatment Options
Most lipomas don’t need treatment at all. Because they’re benign and slow-growing, vets often recommend a “watch and wait” approach: measure the lump, note its location, and monitor it at regular checkups. Surgical removal makes sense when a lipoma grows large enough to interfere with movement, sits in an awkward location, or is growing faster than expected.
For dogs that aren’t good candidates for surgery, steroid injections offer an alternative. In a study of 15 dogs treated with ultrasound-guided steroid injections directly into the lipoma, 9 tumors regressed completely, and the remaining ones shrank enough to relieve discomfort and resolve lameness. Side effects were mild: some dogs experienced increased thirst and urination for about two weeks after treatment. This approach works best for lipomas that are causing functional problems but don’t necessarily warrant general anesthesia.
Reducing Your Dog’s Risk
Because the underlying cause of lipomas isn’t fully understood, there’s no guaranteed way to prevent them. But the research points clearly toward weight management as your best tool. Keeping your dog at a lean body condition throughout their life dramatically lowers the odds. For breeds with known predisposition, this is especially important.
Regular physical checks at home help too. Run your hands over your dog’s body every few weeks so you notice new lumps early. Most will turn out to be harmless lipomas, but catching the occasional lump that isn’t one is worth the habit.