“No, no, no, fatty tumors have nothing to do with your dog’s weight,” I reply to my client with her 8-year-old, yellow Labrador retriever. Lipomas, (pronounced lie-poe’-muss) also known as “fatty tumors,” are common in many older dogs, especially retrievers. Every day in our practice we recheck one or find a new one. Lipomas are sneaky by nature; they seem to show up for no apparent reason (much like the fat on us). Usually our clients will say that they just noticed this new lump even though they pet their dog all the time. Groomers will often find these lumps too.
Lipomas are a benign clump of fat between the skin and muscle layers of the body. The best way I can describe lipomas is that they feel like clumps of firm Jello. They are smooth, usually round or oval, and not attached to the skin (you can actually slide the skin over the top of the growth). They can be grape-sized to several inches or more across. The average one we see is probably the size of a golf ball cut in half. Lipomas are typically found on the chest and abdominal wall. When they do show up, they often remain the same size forever, though some will continue to grow. Again, lipomas are not indicative of a weight problem.
Definitively diagnosing a lipoma can get a little tricky. Sometimes lipomas are under a layer of muscle which makes them feel harder. We use the same criteria as physicians do when evaluating lumps in people. We are more concerned with growths that change, rupture, bleed, become hard, grow or become cluster-like. Besides using history and physical findings, we can use a needle to take cells from a growth and with a microscope look for tumor cells. This is called a fine needle aspirate (FNA). We can also surgically remove a piece of a suspicious growth for a biopsy. Oftentimes it is easier and less expensive to just remove the lump and send it in for histopathology for a diagnosis.
Since lipomas are benign and won’t spread to other organs, it is ok to monitor them. However, we do like to remove rapidly growing lipomas, especially if they are located in the groin or armpit where they can cause problems with movement. The largest lipoma I have removed was bigger than a football, took two hands to hold, weighed several pounds and came off the side of a 40-pound spaniel. This poor dog actually walked leaning over from the weight of this huge chunk-o-fat. Once they get their first lipoma it is likely they will develop more.
There is also a malignant form of the lipoma called a liposarcoma, which tends to grow faster and invade adjacent tissues. Remember, lipomas are soft, benign fatty tumors, but not all soft tumors are lipomas. There are other tumors that can mimic a fatty tumor but be malignant. It always best to have any suspicious lump checked by your veterinarian.
Now, let’s talk about your dog’s weight. “Seriously, did you just call my dog fat AGAIN”?