One of the most frequent presenting complaints we see on our appointment schedule is “Check lump”. Our feline and canine fuzzy friends commonly develop lumps, bumps, warts, scabs and growths of all shapes and sizes. Some of these are simple to diagnose and clearly benign (like an embedded tick) while a small percent of skin growths can be cancerous tumors. It’s essential to have any new lump checked out promptly, to ensure it’s not malignant.
The most important thing that our clients need to understand when we are evaluating Fido’s newfound lump: it is impossible to definitively diagnose a skin tumor without an aspirate. Just looking at a growth, we may make a guess as to what it could be (and granted, it’s an educated guess, but even the educated can be incorrect on occasion); however, we cannot definitely diagnose a lump without an aspirate and/or biopsy.
A fine needle aspirate is just as it sounds. This simple, quick procedure involves the introduction of a small needle into the lump, and then an evaluation of the needle contents under the microscope. Some skin lumps are easily diagnosed (such as lipomas, one of the most common benign skin tumors we see), while other ones may be more challenging and require the trained eye of a pathologist. I aspirate the vast majority of lumps that I see, and microscopically evaluate them all myself; I can diagnose a percentage of skin tumors, but often recommend we submit the microscope slides for definitive analysis by a board-certified veterinary pathologist.
The advantages of aspirates are that they are minimally invasive, do not require sedation or anesthesia, do not cause significant discomfort and are reasonably cost-effective. With fine needle aspirates, we get a definitive diagnosis the majority of the time. The major disadvantage of aspirates is that they only yield a definitive diagnosis about 70 percent of the time; sometimes there is not enough cellular material on the microscope slide for a pathologist to make a diagnosis. In these cases, if we are sufficiently concerned about the mass, we will recommend a biopsy. The other disadvantage of aspirates is that we cannot safely perform them in certain locations (think eyelids, noses and lips) in some of our patients without sedation; I could do much more harm than good if I tried to stick a small eyelid mass with a 22-gauge needle in a “spirited” Labrador!
If an aspirate does not provide the diagnosis, or if a mass has a concerning visible appearance, then sometimes we will recommend a biopsy. There are several types of biopsies available: needle, punch, incisional and excisional. Realistically, the type of biopsy we perform most often is an excisional biopsy, where we surgically remove the growth and submit it in its entirety for diagnosis by a pathologist. (Needle biopsies have some of the same limitations as aspirates, and incisional or punch biopsies involve only taking a piece of the lump, which still requires surgery and sedation/anesthesia, so we might as well remove the whole thing and do an excisional biopsy!) The major advantages of biopsies are that they almost always provide a definitive diagnosis, and, in some cases, can also provide a surgical cure by excising the mass altogether. The downsides of excisional biopsies are that they are minimally to moderately invasive and can result in some discomfort (which we manage with pain medication), they require sedation or anesthesia, and they result in a surgical incision with sutures.
Sometimes, a mass may have a very characteristic appearance and location (such as a viral papilloma, which was the subject of a previous blog), lending itself to an assumptive diagnosis. With these cases, I might not recommend immediate aspirates to confirm the diagnosis and may advise a client to monitor it at home, particularly if the mass is in a difficult location. Benign masses typically do not grow or change rapidly; malignant masses can wax and wane in size, or steadily grow.
If Fido has a mass that is growing rapidly (within days or weeks), if it looks red/purple and inflamed, or if he is bothering it, all these are indications to have the mass evaluated and/or aspirated. My dermatologist removes and biopsies any freckle that has a remotely suspicious appearance; we try to follow similar principles with our own patients. Every veterinarian has been fooled by a mass that had a benign appearance, but was ultimately diagnosed to be a malignant process on further workup. It’s always better to have more information to make the best decisions for Fido and Fluffy. Trust me- if your veterinarian recommends an aspirate or biopsy, we have a good reason to do so!