A lipoma is a benign (non-cancerous) tumor made of fat cells that grows under a dog’s skin. It’s one of the most common tumors found in dogs, typically showing up as a soft, rubbery lump on the torso or limbs. Most lipomas are harmless and slow-growing, but they’re worth understanding because not every fatty lump stays simple, and a few look-alike masses can be more serious.
What a Lipoma Looks and Feels Like
A typical lipoma sits just beneath the skin and feels soft, rubbery, and somewhat movable when you press on it. Most form inside a thin capsule that keeps them self-contained, which is why they tend to stay round or oval-shaped as they grow. They’re most often found on the chest, belly, and legs, though they can appear almost anywhere on the body.
Lipomas grow slowly, sometimes over months or years. Many stay small enough that a dog doesn’t seem to notice them at all. Others can eventually reach the size of a grapefruit or larger, especially in big breeds. A lipoma that grows large enough near a joint or between muscles can start to restrict movement or make your dog uncomfortable, even though the mass itself isn’t cancerous.
Which Dogs Are Most at Risk
Lipomas overwhelmingly affect middle-aged and older dogs. A large study of UK dogs found that those between 9 and 12 years old were over 17 times more likely to be diagnosed with a lipoma than dogs aged 3 to 6. Roughly 2% of all dogs in the study were diagnosed with at least one lipoma in a single year, making them genuinely common in veterinary practice.
Certain breeds are more susceptible. Labrador Retrievers, Springer Spaniels, Dobermann Pinschers, and Weimaraners all show higher rates. Overweight dogs also develop lipomas more frequently, though the exact reason remains unclear. The underlying cause of lipomas isn’t fully understood in any breed. There’s likely a genetic component, but no single gene or trigger has been identified.
How Lipomas Are Diagnosed
When you bring your dog in with a new lump, the vet will typically start with a fine needle aspiration (FNA). This involves inserting a thin needle into the mass, drawing out a small sample of cells, and examining them under a microscope. Fat cells from a lipoma have a distinctive appearance, and in most cases the vet can confirm the diagnosis within minutes during the same visit.
The limitation of FNA is that it can’t always distinguish a simple lipoma from its more problematic relatives. Infiltrative lipomas, which grow into surrounding muscle and tissue, and liposarcomas, which are a rare malignant fat tumor, can look identical to a regular lipoma on a needle sample. A few other tumor types, including a vascular tumor called a hemangiopericytoma, can also mimic the rubbery feel and fatty appearance of a lipoma. When a mass behaves unusually (growing fast, feeling firmly attached, or recurring after removal), a surgical biopsy may be needed to get a definitive answer. Diagnostic testing including biopsies and related lab work typically runs $100 to $400 depending on the clinic.
Simple Lipomas vs. Infiltrative Lipomas
The vast majority of lipomas are “simple” lipomas: encapsulated, slow-growing, and cured permanently if surgically removed. About 8 to 9% of lipomas, however, turn out to be infiltrative. Instead of staying neatly wrapped in a capsule, infiltrative lipomas weave between muscle fibers, along nerves, and sometimes into bone. They’re still technically benign, meaning they don’t spread to distant organs, but they behave more aggressively in the area where they grow.
Infiltrative lipomas are harder to remove completely because their edges blend into normal tissue. They tend to grow faster than simple lipomas and have a higher recurrence rate after surgery, sometimes requiring repeated operations. The body wall and limbs are common locations. Importantly, the diagnosis often depends on what the surgeon observes during removal, since the fat cells themselves look normal under a microscope. It’s the pattern of invasion into muscle and connective tissue that identifies them as infiltrative.
When Removal Makes Sense
Most simple lipomas don’t need to be removed. If a lump is confirmed as a benign lipoma, is small, and isn’t bothering your dog, the standard approach is to monitor it over time. You can track its size at home by measuring it periodically or simply noting changes in shape, firmness, or how quickly it seems to be growing.
Surgery becomes a practical consideration when a lipoma is large enough to interfere with movement, sits in an awkward location like the armpit or groin where it presses against joints, or is growing noticeably faster than expected. Some owners also choose removal when a lipoma is still small because smaller masses are easier and less expensive to excise, with faster recovery times. This is especially relevant in breeds prone to developing multiple lipomas over their lifetime.
For infiltrative lipomas, early and aggressive surgical removal offers the best chance of preventing recurrence. Because these masses don’t have clean borders, the surgeon needs to take wide margins of surrounding tissue, which can be more complex and costly than removing a simple lipoma. In cases where complete removal isn’t possible due to the location, radiation therapy is sometimes used to slow regrowth.
What About Liposarcoma
Liposarcoma is the malignant counterpart to a lipoma, but it’s rare. Unlike a typical lipoma, a liposarcoma is cancerous. The encouraging detail is that liposarcomas tend not to spread (metastasize) to distant organs, but they do aggressively invade the tissues around them. They require surgical removal with wide margins and carry a higher risk of local recurrence.
Because a liposarcoma can feel and look just like a lipoma on physical exam and even on a needle sample, any lump that grows rapidly, changes in texture, or comes back after removal warrants a full biopsy. The distinction between a harmless lipoma and a liposarcoma is made under a microscope by a pathologist examining a tissue sample, not just individual cells.
Living With a Dog That Has Lipomas
Dogs that develop one lipoma often develop more over time. It’s not unusual for an older Labrador or Springer Spaniel to carry several lipomas at once, and this alone isn’t cause for alarm. The practical approach is to have each new lump checked when it appears, keep a simple record of its location and size, and flag any changes at your dog’s regular checkups.
Maintaining a healthy weight may help. Overweight dogs develop lipomas at higher rates, and while weight loss won’t shrink an existing lipoma, it can make masses easier to monitor and may reduce the likelihood of new ones forming. Lipomas don’t typically cause pain, so a dog carrying a few small ones generally lives a completely normal, comfortable life.