I have been getting questions about the best way to gather info about growths in dogs. So, let’s take a look at a common technique used to accomplish this…a fine needle aspirate.
First of all, a fine needle aspirate is not a biopsy. A fine needle aspirate is a sample of the mass taken with a skinny little needle (meaning, not much to work with). The vet will disinfect the surface of the site to be aspirated, often after clipping the hair, to prevent infection. Next, a needle is introduced into the area of interest, and the plunger drawn back, creating a vacuum which draws cells into the hub of the needle. These cells are then used to make a slide for the vet or a pathologist to look at for a diagnosis.
What is good about this technique? Well, it takes about 2 minutes to do, and your dog gets to go home without sedation, anesthesia, or hospital stay. Quick, easy, outpatient…nice. This is a good technique to diagnose TYPE of growth (in my hands about 75% of the time you get this info from the path lab after submitting the slide).
How about downsides? A fine needle aspirate cannot tell if the cancer cells have moved inside the body or spread into neighboring areas. There is a little inaccuracy in this technique as well. My experience is that about 1 out of 4 of these come back “inconclusive”, meaning there was not enough on the slide for the path folks to give a diagnosis. Sometimes the vet will get a big sample, but the cells are just not the right kind to make a diagnosis (blood, connective tissue, etc.). Some tumors have a good cell yield, and others do not. Occasionally, we get an incorrect diagnosis with a fine needle aspirate.
Some dog tumors easily diagnosed with fine needle aspirates:
Mast Cell Tumors
Short story, this technique is a good, non-invasive, rough screen to get initial information. Just keep in mind the limitations…it is not guaranteed and if there is any doubt in your vet’s mind, go for the real biopsy…coming up!