A Big Lump of Fat

Scooby is an older Rottweiler, and as such, had a few problems to deal with today. She has always been a little lame on her hind legs, off and on for years, attributed to likely hip dysplasia so common in the breed. Lately she has actually been holding her left hind leg up, not putting weight on it at all if she could help it. Because of her age, visions of Chloe and her bone cancer came to mind, and I sure didn't want to go there.

Scooby also had a very large mass or lump under the skin over her right shoulder. It has been there for some time, but because she is shifting so much of her weight to her front end (a normal dog will carry 70% of their body weight on their fore limbs-Scooby, with her painful hind limbs, was likely carrying 80 or 90%) this large mass was starting to inhibit the range of motion of her shoulder. It was harder for her to get up and down-and at almost 100 pounds, it would be very difficult for her owners to help her. We needed to find out what this mass was before we could decide what to do about it.

An FNA or fine needle aspirate is a test we can do right in the exam or treatment room of the hospital. It only takes a few minutes on a cooperative patient. We take a very small guage needle, thinner than those typically used to administer vaccines to pets, and aspirate or "suck" cells or fluid or other material from the mass. This material is then put on a microscope slide, it may or may not be stained, and is examined for identification of the type of tissue comprising the mass. In Scooby's case, we aspirated a thin, clear, oily material-fat. Scooby had a giant lipoma or fatty tumor.

Lipomas are very common soft, moveable, round lumps under the skin. They usually don't bother the pet-owners only notice these lumps when they are petting or grooming the pet. They are benign masses, not metastasizing or spreading to other organs in the body although it might seem like they do since pets can get many of them throughout their lives. Verbal has quite a few of these lipomas, most on her ventral or lower chest and belly, but they can occur on legs and tails and even internally in animals as well as people. They are more common in middle-age to older animals, and over-weight females may be pre-disposed to them. Cats and younger dogs can certainly get them, too. Any new lump or bump on your pet should be evaluated by your veterinarian, even if it looks and feels just like a previosly dignosed lipoma, since they can mimic more serious cancerous masses such as mast cell tumors. An FNA such as we performed on Scooby, or even a biopsy may be necessary.

Large lipomas like Scooby had can be very vascular masses, having numerous large blood vessels which make the surgery more of a challenge. It was important we knew what her metabolic status was, the functioning of her organs before anesthesia as this was likely to be a long procedure. We also wanted to know just what was going on with her hind limb lameness and whether it was a treatable or just manageable condition. It would be awful to put her through a big, traumatic (and expensive) surgery only to find she had a malignant bone tumor or something. Thankfully, that wasn't the case for Scooby. She had pretty severe degenerative joint changes in both of her stifles (knees) and both of them had excessive "drawer" motion. By now, reading this blog regularly you know what that means-Scooby had long-standing ACL or anterior cruciate ligament ruptures. Her hip, which her owners always assumed were the source of her pain, were just beautiful on those x-rays! No signs of arthrits or degenerative joint disease there, no remodeling of the femoral heads, good seating of the "ball" into the "socket," and most important, no evidence of bone cancer.

Now Scooby's owners want to do what they can to help make her comfortable but unfortunately won't be able to afford knee surgery (much less two of them) for her. They haven't tried any joint supplements or NSAIDs, let alone narcotics, so we can set her up for our "multi-modal" analgesia plan, just like I have Verbal on. This morning we did the surgery to remove the large lipoma-and it was quite a procedure. There were lots of vessels as I had suspected, but it was also very invasive in the adjacent tissues, seeming to grow into the muscle and fat layers and even right on the ribs themselves. I don't like these "infiltrative lipomas" because it is very difficult if not impossible to be sure you removed all of the abnormal tissue, thus making recurrance likely. Lipomas regrow in about 50% of these cases. It is possible to do adjunct therapy such as radiation to inhibit the regrowth, although this is very expensive. Chemotherapy is useless for infiltrative lipomas. At least we have "de-bulked" the mass, allowing for freer, more normal function of Scooby's shoulder as she puts more and more weight on her front legs. And we are left with a big lump of glistening white fat-anyone for a reverse liposuction procedure?

Peace,
DrReneigh