Pinky Gets a Tumor: Fine Needle Aspirates and Punch Biopsies in Vet Medicine
Posted Sep 21 2010 5:30am
Big, small, aggressively ugly, or seemingly innocuous, all lumps must be addressed. No, it’s never enough just to watch and wait. Sure, you might choose to do so, but only after thinking long and hard about what you’re choosing to leave behind.
And yet removing a mass may not be strictly necessary. At least, not immediately. Hence, why poking or prodding them with needles and blades is often employed as an intermediate step.
I thought of offering you this post after enduring the week-long stress-fest over my foster dog, Pinky, who just endured her own week with the rapidly-rising lump from hell. Caution: Many bumps, needles and punch biopsy-blades are in attendance, so those with queasy bellies beware! Here’s the story
It didn’t look good. In fact, it looked horrible. At first I though it was a simple cyst, the kind of thing that sometimes happens over bony protuberances when dogs bang themselves up against hard surfaces. But it was so hard! So fast-growing! So painful! And so firmly attached to her rib! Then came the swelling, below, and all the pooling of fluid beneath it. Eeek!
Here's another pic (double-eeek!)
After the tears (despite her youth, I was quickly convinced it was some horrible bone or cartilage cancer), I did what everyone should do under these circumstances: I took her to the vet (in this case, me).
Once there, I took a couple of X-rays to check if the bone was obviously involved. It was not. (Whew!) But that in no way meant we were off the hook. I then anesthetized her and performed two procedures we employ to identify the masses: a fine-needle aspirate and a punch biopsy.
A fine needle aspirate (sometimes called a "fine needle biopsy") involves a simple but scripted series of jabs with a 22-gauge needle, followed by its expulsion onto microscope slides, where, once stained, cells identifying the mass might be observed.
It’s a quick and dirty way to detect many kinds of cancers, either immediately in the hospital or by sending the slides out to a pathologist. While most veterinarians prefer to use pathologists for this, the cost factor often means that in-house observation is as far as it goes. And sometimes that’s perfectly all right — especially when we’re using the fine needle aspirate as a simple screening test before undertaking a complete excision and subsequent biopsy.
Here are questions we’re hoping a fine-needle aspirate will answer for us: What kind of cells are there? Do they look angry? How angry? Should we remove this mass? If so, how? Should we get a larger sample first (punch biopsy) or go straight to a complete excision? Is it best at this point to refer the patient to a surgeon? To an oncologist?
Problem is, a fine needle aspirate can only look at individual cells, not the architecture of tissue. It only gives us a tiny tease of what’s there. Sure, we’re hoping the cells we see are representative of the whole mass but we can’t exactly assume that’ll be the case every single time. And sometimes the mass doesn’t even "exfoliate," which means it doesn’t give up the cellular goods into the needle, as we might have hoped.
A punch biopsy, while more invasive, is a whole lot more helpful. Because we’re actually "punching out" a bit of the mass with a tool reserved for this purpose, the tissue remains intact so that its cells and their arrangement within it can be observed. Given that we’re only looking at a fraction of the mass, this procedure also has its limitations. Complete excision is the only way to be 100 percent sure of the mass type, and even then pathologists may disagree...
In case you’re wondering, a fine needle aspirate typically does not require anesthesia. However, in Pinky’s case there were two issues: 1) the mass was painful, and 2) I was planning the punch biopsy regardless of my fine needle aspirate findings — and that usually does require heavy sedation, at the very least.
So why do two procedures to ID the mass?
In situations like Pinky’s, the goal of the fine needle aspirate is to have something to look at in the hospital — for my own eyes, to get an inkling of what I might be expecting the pathologist to tell me about my punched-out tissue sample.
Why not remove the whole thing, you ask?
Just look at it. To remove the whole thing I would have had to remove a rib. I want to know what it is before I go digging around in there. Getting a piece of it was all I needed at this point. After all, if it’s an aggressive cancer in that location, I want CTs and MRIs and such before committing to a surgical approach — one for which I will not be playing the lead surgeon.
Yes, there are very good reasons why a punch biopsy is a preferred first step in lieu of a complete excision.
1. Because identifying the tumor type and its typical activity is crucial to knowing how carefully you need to go about removing it.
2. Because you may not need to remove it at all.
As it turned out, Pinky’s mass did NOT need to be removed. A course of antibiotics eventually resolved what ended up being an impressive reaction to an infection. All I’ve got to deal with now, a full week later, is one little stitch that’ll come out on Friday. Now I can breathe a sigh of relief. That would not have been so without the saving grace of my little green friend, the punch biopsy blade.
Thank God for small, wonderful tools!
Dr. Patty Khuly
P.S.: Pinky still REALLY needs a new home! Look at that face! How can you say no? Well … my chickens do. They don't like the chasey-chasey game.