Benign Fatty Tumors in Dogs

Updated May 25, 2017

You notice your geriatric dog has developed a round lump on her side, and, upon examination, your vet diagnoses a lipoma---a benign tumour composed of adipose (fatty) tissue and cells. Talking with your veterinarian and learning all you can about lipomas, and how they can affect the health of your pet, will allow you to decide the best treatment and care for your animal.


Veterinarians identify a typical lipoma by feel, when a dog presents with a well-defined, soft mass directly under the skin. Upon palpation, lipomas move freely without attachment to muscle tissue and appear as one solid mass. These tumours vary in size, and grow slowly, often taking on an oval or round shape visible to the naked eye. The infiltrative type of lipoma grows in between muscle layers in deeper tissues and remains attached to the muscle wall.


Your veterinarian might suggest pulling a fine needle aspirate by inserting a thin needle attached to a syringe into the mass and extracting a number of cells. A technician expels the cells onto a glass slide, stains the slide to fix the cells, then examines the slide under a microscope. If the fat cells have not fixed and are no longer on the slide, veterinarians typically make a presumptive diagnosis of lipoma, says Dr. Alleice Summer in her book "Common Diseases of Companion Animals." An excisional biopsy yields a conclusive diagnosis.


Because a lipoma is benign, many veterinarians will recommend treatment only when the tumour grows large enough to cause pain or discomfort to your dog, states Dr. Douglas Brum of Your vet may suggest surgical treatment if the tumour is particularly fast-growing or interferes with your dog's ability to walk or lie down. With a common lipoma, dogs require general anaesthesia and many vets will suggest preliminary blood work due to the age of the patient. An infiltrative lipoma necessitates a larger, wider incision, and your vet might not be able to remove all of the cells.


Because lipomas are benign, meaning they are not cancerous, vets consider the prognosis for a dog diagnosed with this condition excellent. Even though the tumours can grow quite large, surgery cures the problem, says Summers.


Lipomas usually develop in older, overweight female dogs, typically on the trunk and upper limbs, states the Merck Veterinary Manual. Breeds predisposed to the condition include Labrador retrievers, miniature schnauzers, golden retrievers, Doberman pinschers and all mixed-breed dogs. Veterinarians identify a rare type of lipoma, called diffuse lipomatosis, by the prominent folds on the neck and trunk it causes in Dachshunds---the only breed this tumour seems to affect.


The infiltrative type of lipoma often proves difficult to remove and may recur after removal, says Because it affects the surrounding muscles, recovery time may be slower and more painful, with bruising and fluid retention developing at the surgical site.

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