Lipomas: Benign Fatty Growths
Joe Bodewes, DVM
Veterinary Services Department, Drs. Foster & Smith, Inc.
Lipomas are one of the most common benign tumors found in dogs. Most older or overweight dogs have at least one lipoma. Almost every dog owner has, at one time or another, found or felt one of these common fatty tumors on their dog. Veterinarians generally disregard these and don't recommend removal unless they are causing a problem. With only a few exceptions, this is generally the advice that I give as well.
What are the characteristics of lipomas, and how are they diagnosed?
I regularly advise dog owners to bring their dog in for an examination if they find a growth that suddenly appeared. I usually take a history of the dog and do a careful palpation of the growth. If I suspect a lipoma, I document the size and location and then recommend that we keep an eye on it and only become concerned if it grows rapidly or starts to become too large and create a problem with mobility. I usually offer to perform a fine needle aspirate or biopsy to confirm that it is a lipoma.
When I talk about lipomas, I try to avoid the word 'tumor' in the conversation. When most people hear the word 'tumor', a big red flag goes up in their mind and gloom and doom scenarios take over. I like to call these fatty tumors, "growths" and often describe them as fat deposits in an abnormal location. They almost always are located in the subcutaneous tissue. They are firm yet moveable and they are painless and not associated with infection or hair loss.
Treatment
While I and every other veterinarian have probably removed lipomas for cosmetic reasons, we usually discourage it because the slight risks associated with anesthesia and surgical complications are not worth the health benefit of removing a common growth that will not cause any problem. We may suggest that if the animal is going to anesthetized for another reason, e.g.; dental cleaning and polishing, the tumor(s) could be removed then. The other reason they are usually not removed is that they are so common, a veterinarian could fill his or her entire day with the diagnosis and surgical removal of these tumors and never get anything else done. Monitoring their size and removing them if they are impeding mobility or are causing friction rubs between the flank and leg are all that is usually necessary.
With this said, I want to caution owners against routinely dismissing growths or lumps in the skin or subcutaneous tissue. There are some very serious tumors that appear in the skin and subcutaneous tissue and it takes a trained veterinarian to distinguish between them. I always encourage pet owners to bring their dog in for an examination whenever they identify a new growth or lump. A fine needle aspirate or biopsy can easily be performed to verify the existence of a lipoma.
While simple lipomas are the most common, occasionally a more infiltrative lipoma will develop. These lipomas invade the surrounding tissue to a greater degree and will regrow about half of the time after they are removed. This is just another reason that veterinarians are often reluctant to remove these tumors. These infiltrative lipomas are not more aggressive or dangerous, they are just harder to successfully remove.
Summary
If you find a lump on or under your dog's skin, have him examined by a veterinarian. Your veterinarian can determine if it is a lipoma and can verify it with a fine needle aspirate or a biopsy. Surgical removal is the treatment, but usually isn't necessary because these growths are benign and rarely become overly large.
References
Ettinger, S; Feldman, E. Veterinary Internal Medicine 5th Edition. Published by Saunders. Philadelphia; 2000.
Bonagura, J; Kirk, R. Current Veterinary Therapy 12. Published by Saunders. Philadelphia; 1995.
