When my friend, Dr. Jennifer Shepherd, suggested a blog post on lipoma in dogs, I was fully on board. Lipomas are common in older dogs, so I thought it would be a great help to our readers. Little did I know how helpful it would turn out to be! When she volunteered to write it, I asked her to take pictures and demonstrate fine needle aspiration (FNA) of a lipoma on video. Later she messaged me this: “I may have saved a life thanks to you! I saw a dog today and the owner said that the lumps had been looked at before. So I assumed one was previously diagnosed as a lipoma. I decided to aspirate just to make a video for you. Turns out it’s probably soft tissue sarcoma. I’m removing it on Wednesday.”
If your older dog is “lumpy and bumpy,” lipomas are a common culprit. Read on to discover how we diagnose lipomas and avoid misdiagnosing lipomas. I hope you’ll find peace of mind reading Maggie’s true story and learning what to expect if your veterinarian suggests a fine needle aspirate for your dog’s suspected lipoma (spoiler alert: it’s no big deal.) 🐾
~Dr. Julie Buzby, Founder of Dr. Buzby’s ToeGrips for Dogs
A mass the size of a softball
Mrs. Anderson was worried about Maggie, her 12-year-old Pit Bull mix.
Maggie had always been in good health, but over the past couple of weeks, she seemed relentlessly plagued by a nagging cough. Adding to Mrs. Anderson’s anxiety, the softball-sized mass on Maggie’s chest that she had discovered six months prior appeared to be growing. Day after day, one thought cycled through her mind: Could the mass in her chest be pressing into her lungs and causing the cough? Even more fundamental—what was this mass?
Mrs. Anderson scheduled an exam for Maggie. It wasn’t hard to find the mass on my exam. It was almost five inches in diameter, soft, and located just under the skin on top of the muscle. Although I thought I knew what it was, I ordered X-rays to reassure Mrs. Anderson and to get to the bottom of Maggie’s cough and congestion.
The X-rays confirmed my suspicions. The source of Maggie’s cough was bronchitis—and while the mass was there, it was outside of the chest wall, growing away from the chest cavity. Mrs. Anderson was visibly relieved.
Next, to put to rest all of Mrs. Anderson’s fears, it was time to investigate the softball-sized growth. In Maggie’s case, based on the shape and feel of the mass, I strongly suspected it was a lipoma.
What is a lipoma?
A lipoma is a benign tumor of the fat, or adipose tissue, usually with well-defined boundaries. Lipomas typically do not invade the underlying tissue and are found just below the skin.
What causes lipoma in dogs?
It is uncertain what causes lipomas. As with many conditions, the causes are often multifactorial with environmental and genetic factors likely playing a role. Lipomas are more commonly seen in senior dogs but can occur at any age.
How do you diagnose a lipoma?
A lipoma diagnosis can’t be made by a physical exam alone. This is a critical point. Even a board certified veterinary oncologist cannot diagnosis a lipoma by looking and feeling. A fine needle aspiration, extraction of cells for evaluation, is needed to rule out other below-the-skin tumors that can be of far greater concern such as mast cell tumors and soft tissue sarcomas.
Fine needle aspiration
A fine needle aspiration is a simple diagnostic test typically performed in the exam room on an alert and conscious dog. Although perhaps unsettling for owners since a needle is involved, most dogs remain calm and react to the procedure no more than they do when receiving a vaccine.
To perform a fine needle aspiration, your veterinarian inserts a needle into the mass, redirects it multiple times to gather cells, and then removes it with a sample of the tumor’s tissue. In the video below, a veterinarian demonstrates a fine needle aspiration on a dog.
As you can see in the video below, the collected material is then smeared onto a slide using an air-filled syringe and examined under a microscope.
Microscopic characteristics of lipoma in dogs
When stained and observed under a microscope adipose or fat cells, and sometimes red blood cells are visible. Because lipomas are mostly fat cells, the material on the slide often looks like oil.
If these are the only types of cells present, your veterinarian can confidently make a lipoma diagnosis.
How are lipomas treated?
Like Mrs. Anderson, many dog owners find masses on their dogs and become concerned that their dog has cancer or that the mass is going to compress vital organs. But lipomas are almost always asymptomatic and usually do not cause any physical problems.
In some cases, they can grow large and, based on location, interfere with your dog’s mobility. In those situations, lipomas can be surgically removed. It’s important to note that the surgical removal of one lipoma does not prevent another lipoma from developing in a different area.
FAQs about lipomas in dogs
Q: Are lipomas harmful?
A: Most lipomas are harmless and do not cause any symptoms. However, if they grow in the abdominal cavity or the spinal canal they can compress other organs and cause clinical abnormalities. Occasionally dogs may develop an intermuscular lipoma—a lipoma that grows between muscle layers. This type of lipoma most commonly occurs in the back of the thigh and causes lameness.
Q: Can lipomas turn malignant?
A: Lipomas are not malignant and cannot become malignant. There is a very rare malignant tumor of fat cells called a liposarcoma that is locally invasive and often spreads to other parts of the body. However, liposarcomas are not tumors that began as lipomas; they are completely different.
Q: What should I do if I find a lump on my dog?
A: If you find a lump on your dog, you should schedule an appointment with your veterinarian. Your veterinarian will most likely aspirate to determine if the mass is a lipoma or another tumor that should be surgically removed.
If your dog has multiple masses, it’s helpful to have a “body map” showing the location and size of all the masses on your dog. This will allow you to determine if a mass is new or if an older mass has grown in size. Your veterinarian will likely keep one in your dog’s medical record, but you can keep one in your dog’s health journal also to note changes at home.
Q: My dog is covered in lipomas, and I just found another one. Does it need to be aspirated?
In short, probably. Let me explain with a story.
Chloe is a 9-year-old Black Lab who had been previously diagnosed with a handful of lipomas.
When she came in for her annual exam, I found a quarter-sized mass in front of her shoulder. (The importance of annual exams cannot be overstated.)
Scanning her records from last year, I didn’t see a mass noted in this location. Although it felt like a lipoma, I wanted to be thorough.
I performed a fine needle aspiration to collect a sample.
After smearing it on a slide, I saw the classic oily appearance with what appeared to be blood cells mixed in. Upon examination under the microscope, however, the material that looked like blood was actually a mixture of red blood cells and neoplastic (cancerous) round cells. Maggie’s new mass was not a lipoma—it was a soft tissue sarcoma. I advised surgical removal at the next possible opportunity.
If you find a new lump on your dog that hasn’t been previously documented, it’s always a good idea to discuss it with your veterinarian.
Common in senior dogs
Lipomas are very common tumors in senior dogs. And while I have had clients tell me that their dog is filled with cancer after seeing multiple lipomas develop, more often than not, these masses are nothing more than harmless lipomas and unlikely to be causing any negative health symptoms.
As always, though, make an appointment with your veterinarian anytime you observe something new or “off” with your dog—just like Mrs. Anderson, it’ll help you put your worries to rest or allow for early diagnosis and treatment of genuine concerns.
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