Fatty lipomas are nothing to worry about
Q: I found a lump on the side of my dog, Candy. It was the size of a grape and soft. When I touch it, she doesn't cry or run away. When I took her to my vet, he looked at it and said it was a lipoma and not to worry about it. What is a lipoma, and shouldn't I take it off? I am afraid it is cancer.
A: Lipomas are very common tumors in dogs and sometimes cats. They occur in middle-aged to older dogs and in many overweight pets, especially old hounds named Nehlen Dascoli. Other breeds besides Nehlen hounds that commonly get them include cocker spaniels, dachshunds, poodles, terriers and Labs.
Lipomas are non-cancerous tumors in the subcutaneous tissue of the skin. They can be found other places, too. They are made up of cells called lipocytes which are a very important part of a dog's body as they are able to store fat that is used as energy for work, food during anorexic periods and as insulation to the cold. Lipocytes can swell enormously to store an unlimited amount of fat and additionally will shrink when fat is needed for the body.
Any tissue cells can grow into a tumor, and fat is no different. These tumors are benign and do not invade other tissues or spread in a destructive way. They grow slowly and stay in one place. That is not to say that a pet can't have multiple lipomas as they age and if they gain weight. This is common to find multiple lipomas, or "fat balls," as we call Nehlen's.
The best way to diagnose a lipoma is to stick a needle in it and look at the cells under a microscope. This is relatively painless and can be done by any veterinarian. Once a diagnosis is made, yearly monitoring for changes is all that needs to be done. I do not recommend removing most lipomas merely for cosmetic purposes. If a pet is already being sedated for something else then they can be removed if the owner likes, but the pain and possible complications from surgery do not warrant automatic removal.
There are a couple of other types of lipomas that we see rarely. One is an infiltrative lipoma. These are not round and well-defined but have projections and weave around and in between muscle tissue. They can cause functional issues with movement and for that reason most veterinarians may recommend removal. They are more difficult to remove, obviously, and can reoccur if not completely removed.
The third type of a lipoma is a malignant liposarcoma. These are cancerous growths that are difficult to remove and act to destroy tissues. Surgery with very wide margins is the primary way to treat these cancers followed by radiation. A surgical biopsy is needed to diagnose this rare tumor.
If your veterinarian has done a needle aspirate of the tumor on your dog and is convinced it is a benign lipoma, then watching it is OK. I would re-aspirate it yearly at your check ups to make sure nothing changes. If there are no changes, your dog can be like our beloved Nehlen, lumpy and loveable.
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