Does Fine Needle Aspirate Increase Cancer Spread?

Featuring Demian Dressler, DVM and Susan Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide.

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Does Fine Needle Aspirate Increase Cancer Spread?

From time to time in the history of cancer and biopsies, concern arises that biopsies and fine needle aspirates spread tumors.

Like all things medical, the truth is there are always two sides of the coin. Here, we present the bottom line information on fine needle aspirates and tumor spread in loved dogs.

When we perform a fine needle aspirate, we insert a needle and aspirate (suck) cells out. We remove the needle, which leaves a tiny tract (a tunnel) where the needle was.  The cells are next placed on a slide to see if they are cancerous.

So do cancer cells move out of the hole we made with the needle and implant themselves along this tract?

For tumors under the skin, or in the skin, the benefit of a diagnosis far outweighs cancer spread risk.  Fine needle aspirate is almost always a good idea.

For tumors within the abdominal cavity or pericardium (heart sac) that are filled with fluid, we must be cautious that the growths do not leak fluid with cancer cells through the tract.  One can tell if a mass is fluid filled with the ultrasound. The argument to avoid fine needle aspirates in these cases is reasonable, but this is a judgement call that should be left to the vet.

For solid tumors within the body, there is very low risk  of spread along the needle tract (almost always smart to get a specimen for fine needle aspirate with these)…except in the urinary tract.

For growths of the urinary tract  (bladder, urethral or prostate), which in the dog are often transitional cell carcinomas, there are reports of cancer spread along the needle tract of a fine needle aspirate.  Again, the argument to avoid these in general has merit. These can be often be tested using a catheter to collect the specimen as a first step, as opposed to fine needle aspirate. Again, discuss this with your veterinarian.

There is a report of a lung tumor that spread along the needle tract in the dog, but this is only a single report, and thus we need more data before suggesting we avoid fine needle aspirate for lung tumors or solid tumors in the chest cavity.

Sometimes a diagnosis can be reached by taking a piece of tissue for biopsy. This is different as a larger amount of tumor is removed compared to fine needle aspiration.

At this time, we don’t have enough data to suggest that in the dog doing surgical biopsies causes distant spread of cancers. This may change later, time will tell. There are some tumors in other species where biopsy does increase tumor spread odds, but very slightly. For more general information about this topic, this abstract has some good data. The scale tips most definitely in the direction of the biopsy.


Dr D

About the Author: Demian Dressler, DVM

Dr. Demian Dressler, DVM is known as the "dog cancer vet" and is author of The Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog's Life Quality and Longevity.

  • Bill

    Just took my dog to the vet to have a lump examine. Doctor says the lump is too small to aspirate. Is that true? If so, how big does it have to get?

    • Dr. Demian Dressler

      Dear Bill
      I’ve successfully aspirated growths down to about 3/16″ in diameter.
      Hope this helps
      Dr D

  • Mike S.

    Eli, our golden retriever (almost 8 years old), was a really happy dog, who in about April 2012 started having some constipation and straining when defecating. We had taken him to the vet at the time, who put him on some antibiotics at the time. It slightly improved, but he started up again in beginning of June 2012 with the same thing, and took him to the vet again, who looked at the stool, and saw that there was some hair, and they thought that was causing the constipation, and to give him some fiber, which we had done, but with no real improvement.

    Then, all of a sudden, one day, he couldn’t go pee, and had a sort of a deep grunt, which we knew was not normal, and rushed him to the vet yet again. We had also noticed some inflammation near his penis (they said it was adema). This was around July 25, 2012, and they did several x-rays, followed by an ultrasound, and suspected a prostatic carcinoma (as they saw some mineralization in the prostate). They started him on Rimadyl right away, as they didn’t have piroxicam readily available. A few days later, we say the oncologist and he did a fine needle aspirate of the prostate with ultrasound guidance. He was diagnosed with TCC of the prostate the next day around August 1, 2012. About that same day, we started him on piroxicam (of course NOT along with Rimadyl), but the adema never really got better.

    He was on piroxicam for about 2 weeks, and we had our first chemo session scheduled soon thereafter. However, a few days before we even started chemo, his back right leg started swelling up pretty bad, and we had to take him into the vet the day before the chemo session, as it just kept getting more swollen. The doctor did another ultrasound, and saw that the TCC had spread to the lymph nodes (who knows where else).

    They did the chemo (mitoxantrone) the next day, as the doctor felt that we could see some improvement (possibly decreased swelling in the leg) with the chemo treatment. We also had him on tramadol to help with the pain and discomfort. However, the swelling never really went down, as his leg was very swollen still after chemo, and he really was unable to walk around, now robbing his mobility, while now having a much much harder time defecating (i believe the sublumbar lymph nodes were swollen all along, which i believe pushed against his bowel, making it extremely hard to defecate). Not to mention the chemo made him nauseous, and didn’t have much of an appetite. His quality of life diminished very quickly, quicker than we could have ever imagined. We cherished every day, as we knew things were going downhill. About 5-6 days after the first chemo treatment, we were contemplating ending his suffering, as he was in pain, and the tramadol didn’t seem to be helping much anymore. He lost pretty much all joy in life, and that same night, as he was laying down in his bed, started bleeding from his nose uncontrollably. We had to rush him to the vet again, but this time, knowing in the back of our minds that this would be the last time we would be with him. We had to put him to sleep that night, and the doctor agreed, as the cancer had advanced so quickly and caused other complications.

    It all happened so fast. He was healthy happy dog on July 24, 2012, and died on August 29, 2012. We had done everything possible without being too invasive, but in the end, the cancer got the best of him.

    I just wanted to post this story for anyone else going through this terrible disease. There are others that have gone and are going through it as well, and my heart goes out to each and every one of you. Be strong. Don’t stop spoiling them. And have as much fun as possible in the time you have left, as you just never know when it may be the last day. Keep trying to beat the odds! We can’t let cancer keep winning.

    • Dr. Susan Ettinger

      I am truly so sorry about your loss of Eli. It is never easy. Four years after the loss of my Paige, I still miss her terribly. Try to hold onto the good memories shared through the years to help you through the pain now.
      With sympathy, Dr Sue

  • ww

    We just had a FNA done on a mammary tumor about 2 months ago, and now its larger and also irregular, the vet had to inject multiple times with the same needle to try and get a sample to squirt onto the slide for lab analysis.
    They said that the results came back negative, assuming there was enough sample material on the slide.
    Oddly, the shape of the tumor now, like a “W” reminds me of the multiple stabs of the needle.
    Only time will tell if we made a grave mistake for our 7 year old.

  • Susan Kazara Harper

    It’s often difficult to get tissue into the needle when aspirating. The material inside a lump can be liquid or lumpy itself, so sometimes multiples tries occur. The vet will be doing everything possible to get a good sample of tissue. Is this lump somewhere that it can be taken out surgically? A needle aspirate can possibly tell you what’s inside the lump, but if what’s inside is not benign you’re looking at surgery anyway. The best, ultimate treatment for cancer if it is cancer is to cut it out if at all possible, with wide margins to try to get every cell. If the lump is around the nipple it might be very possible to do this. Ask your vet, and get referred to an oncologist if it’s possible. It’s always best to have an expert in any field. Good luck to you both.