Alicia Pet Clinic Weblog

What’s up with my dog’s fatty tumors?

I was recently asked a question in an “ask the vet” article:

What’s up with Lipomas.  All the dogs I’ve had seem to get them when they get older and some even before they get old.  Veterinarians have told me they are harmless so leave them alone, but some of them get so large that they have to be uncomfortable.  Is there anything we can do or feed dogs to stop them or is there a safe way to remove them so they won’t come back?  My cats don’t get them?   Tara in Aliso Viejo

Tara poses a question that is asked almost every day at Alicia Pet Care Center by dog owners.  Lipomas are benign tumors that derive from mesenchymal cells and primarily affect dogs.  They are the most common tumor encountered by veterinarians and are typically no big deal.  They are more often seen in older female dogs but can affect dogs of both sexes and dogs of all ages.

Lipomas are basically a group of fat cells that grow excessively and eventually make a bump under the skin or rarely under a layer of muscle.  It is extremely rare for lipomas to form on the inside of chest or abdomen, but sometimes they can be more aggressive if they are an uncommon type called an invasive lipoma.  The invasive lipomas are still benign, as they do not spread to distant sites, but they are extremely aggressive locally and can be very difficult to remove.

Another variant of the lipoma is the rare form that is malignant, called the liposarcoma.  This type of tumor is both locally aggressive and can spread to distant sites.  Telling the difference between a lipoma, an invasive lipoma and liposarcoma is very difficult until the mass is removed and sent into the lab for pathologic analysis.  Luckily, the vast majority of these fatty tumors are just that, a bundle of fat that forms a bump.

At Alicia Pet Care Center, our approach to dealing with lipomas is to perform a needle aspirate of the mass and possibly send it into the lab for cytologic analysis.  If the mass is a lipoma, we typically leave the bump alone unless it is in a bad anatomic location for continued growth or if it is growing too big or too fast.  Most lipomas are simple to remove with surgery.

I suggest that if you identify a bump on your dog or cat, that you have the mass evaluated by having a fine needle aspirate performed on the mass.  Many other types of tumors look or feel exactly the same as a lipoma and can prove to be very serious if not addressed quickly.    Also, remember that lipomas are extremely uncommon in cats, which makes a bump very likely to be cancer in this species.

There is no correlation between lipomas and overweight dogs.  At this time, there is no knowledge of anything that can be done to prevent or slow down the formation of lipomas in dogs.


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