Some of you know the drill well: A new lumpy-bumpy pops up, seemingly overnight. You make the appointment, trek to the vet hospital and have your vet stick a needle in it. She then checks the cells she’s extracted under a microscope and sometimes decides to send another slide to the pathologist for examination. She then adds a description of the mass to a chart she keeps that details your dog’s individual topography. 

Most of the time she informs you it appears to be a benign fatty tumor—a lipoma—and you breathe a sigh of relief when she tells you she’d rather not surgically remove it. Whew! A benign tumor requiring no surgery—now that’s good news. All you have to do now is live with its unsightliness, a vision your dog has no reason to resent—he could care less what he looks like.

But if your vet is one of those cautious types, she’ll typically inform you of something you may not know: a “fine needle aspirate” is an inexact method of assessing any given mass’s potential to do harm. It only tells you what the cells look like in the spots within the lump accessed by a small needle. It can’t possibly be 100% representative of every cell within the mass’s confines. Moreover, considering that lipomas are nearly impossible to distinguish from liposarcomas (the cancerous version) on a fine needle aspirate, this far rarer mass is still a distinct possibility.

That’s why some vets are more likely to offer lipoma-like mass removal as the ideal medical option. Indeed, most board-certified veterinary surgeons will recommend it. After all, they’ll argue, you can’t know what it is without examining the whole thing. And you wouldn’t leave any mass on your body without the same assiduous treatment—unsightly or not.

Despite this “purist” approach some extra-cautious veterinarians will take, cosmesis is often cited as the general practitioner's primary rationale behind most surgical removal of presumptive lipomas.

That’s because, it’s true, there’s a low probability that a mass would be cancerous or otherwise harmful if it looks like a lipoma under a microscope. It’s also true that lipomas are notoriously annoying to remove and suffer a high rate of post-operative complications (superficial infections, mostly) and delayed healing—not to mention the expense, discomfort and risks involved in any anesthetic procedure.

One other exception comes to mind for most GPs, however. Should a lipoma-like mass grow in an area where limb movement or other basic bodily functions might be compromised, we’ll remove that mass. But if it’s large and potentially difficult to resect, I’ll always recommend a board-certified surgeon for these tough ones—that is, if my clients are able to shoulder this greater expense.

Luckily, lipomas occur most often on the trunk of a dog’s body, where they’re more easily resected due to the abundance of skin (they’re rare in cats but, interestingly, they’re common in budgies). Older, obese females seem predisposed but no breed predilection has been established. Hence, another good reason to keep you dogs lean.

Are you a bad owner for choosing not to remove these? No way. But you should know the risks. As veterinary medicine advances and begins to approximate human medicine’s standard of care, it may be that no lipoma will be left untreated in the future. For now, though, they’ll remain the red-headed stepchild of the general vet’s surgical repertoire.