Friday, June 11, 2010

What is that lump anyway?

Seems to be a lumpy bumpy kind of week here at the clinic, but I had two of my lump removal surgeries decline a biopsy this week so I thought I would do a little discussion of lumps and bumps that are found on our pets.

First let me say that lumps on or under the skin are REALLY common in dogs. Not so much in cats, but they can get them too. But dogs love to grow lumps and bumps. Fortunately probably 90% of skin bumps in dogs are benign meaning that they don't spread into the surrounding tissue and they don't spread throughout the body. Most benign lumps are harmless, but some can grow quite large and then they can cause a problem. I once removed an 11 pound benign lipoma from the rear leg of a dog that weighed 17 pounds after surgery. The dog sure could walk better after that surgery! The most common lumps I see in dogs are sebaceous cysts (they sometimes can rupture and ooze a cottage cheese like material), sebaceous adenomas (I call these "moles" to use a common slang term and most owners tend to call these "warts") and lipomas (which are fatty tumors that form a smooth lump under the skin).

Now if 90% of lumps and bumps are benign, that would mean 10% are cancerous growths. These growths are more aggressive and have the potential to either invade into the surrounding tissue or spread throughout the entire body. I know the word "cancer" scares a lot of people (heck it does me too), but surgeons all over the world are curing patients from cancer every day. A cancerous lump grows. The lump is removed before any of it spreads. Patient is cured. Now there are aggressive cancers that don't follow this plan, but when it comes to lumps on the skin, those lumps have the best chance for cure because they can be found when they are small.

Before I go any further, I am going to answer the most common question I get in regards to lumps. What causes a lump to grow in the first place? The answer: I don't know. That is the one million dollar question now isn't it? Lots of research going on right now and the puzzle is slowly being solved. But I am the practical sort and for me, it really doesn't matter why a lump grew because I have no means to stop them from growing. What matters to me is what to do about a lump now that it is already here.

Unfortunately, it can sometimes be hard to tell a benign lump from a cancerous lump by just look and/or feel. I'm not going to go into great detail about ways to tell the difference other than to say they vary from needle biopsies to surgical biopsies with some differences in between. But if I feel strongly enough that a lump or bump be surgically removed, then 95.7582% of the time I am going to recommend that the lump be sent to the lab so the folks in the white coats can look at it under the microscope and determine if it is benign or malignant. Now I know that a biopsy is not cheap, but believe me, sending lumps off to the lab is not a big money maker for the clinic. Most of the fee covers how much the lab charges us with a little tacked on to cover the cost of the vet tech preparing the sample to be sent and the doctor interpreting and calling the owner with the results. I can't even say that I am purposely sending business to the lab. I don't even know the folks at the lab. I said they wore white coats, but I really don't even know if that is true or not. What is true is that if I recommend that a lump be sent out to be biopsied, I truly want this information in order to best care for my patient.

But I will sometimes get someone who says that they do not want to know the results because if their dog has cancer, they aren't going to treat it anyway. Fair enough. But let me give you two real life scenarios that I have personally encountered.

#1 A cute little beagle comes in to have a growth removed and it turns out to be cancer. The pathologist says that this cancer is invading into the surrounding skin and that little microscopic fingers of cancer cells are spreading outward and not all of them were removed at the time of surgery. So I go back to surgery and remove more tissue. This time the pathologist says all the cancer was removed. Three years later the dog is cancer free with no recurrence. What if we had not sent the lump out to be tested? The dog would have had its cancer return and maybe spread throughout the body. Then it might be too late to do anything.

#2 Sharpei with an ugly nasty mass on the front of one front leg. I took off the mass and the owner refused to pay for a biopsy. 3 or 4 months later, the mass grew back and she brought the dog in and asked what should be done? Hmmmm? I have no idea what to do because you didn't want the lump biopsied the first time around. So back to surgery, remove the lump again, and this time send it to the lab. Turns out the mass was a kind of deep seated infection that could have been treated with long term antibiotics instead of another surgery. The first biopsy could have saved that dog a second surgery and saved the owner a lot of money.

Now I am not so anal retentive as to say every lump that is removed should be biopsied. I don't send out sebaceous cysts most of the time and known lipomas don't need sent out either. In general though, if a lump is important enough to be surgically removed then it is important enough to find out what is that lump anyway?


  1. Thank you for that this was an interesting read.

  2. Very good topic Doc. I have never had much luck in catching cancer on time with my pets. I take them to the vet for checkups but they are not always found at that time.