Fear of the needle is not reserved to the vaccine hesitant; it extends to biopsies as well. In corners of social media where misinformation accumulates, influencers with an axe to grind against doctors are warning people to stay away from biopsies that help diagnose a cancer. “NEVER do a prostate biopsy, NEVER do a breast biopsy,” you will read, as the biopsy is said to spread the very cancer it is sampling.
Some of these influencers claim they just want patients to be aware of the risk, while others advise against getting any biopsy when cancer is suspected. “This is a setup for Big Pharma’s toxic drugs, chemo, and radiation that guarantee more metastasis,” I personally readĚý.
As with most scaremongering, there is a seed of truth here, but these deranged exaggerations are likely having lethal consequences. They create hesitation and delays, and when a diagnostic biopsy is postponed, cancer, if it is there, is allowed to grow, spread, and worsen.
So, why are doctors so eager to stick a needle inside of us and send a sample to pathology? Because pathologists—the unsung heroes of medical diagnostics who look at innumerable glass slides every day—can use specific dyes (called “stains”) and scrutinize this tissue sample under a microscope to see how it differs from healthy tissue. Instead of well differentiated cells, in the right shape for the role they have to play, they might witness poorly differentiated ones. The insides of each cell may also look abnormal, and receiving samples of nearby lymph nodes will allow them to see if the cancer has started to spread beyond its origin.
This crucial diagnosis, provided to the oncologist by the pathologist, informs treatment. An oncologist can decide on the approach to take, and whether to administer chemotherapy before or after surgery, for example.
Biopsies can be done in different ways, depending on the cancer that is suspected and on the location of the mass of tissues that may be cancerous. A fine needle aspiration uses a very thin needle; a core biopsy uses a bigger one. Biopsies can be done through the skin, but they can also be done through endoscopy, when a tube is inserted inside, for instance, the digestive tract.
But as the needle pierces through a tumour and is then retracted out of the body, the concern is that cancerous cells from that tumour may be seeded along the path of the needle, much like how a similar needle would leave a trail of custard as it is pulled out of a Boston cream donut. This is known as needle tract seeding (occasionally written as “track” instead of “tract”).
The good news is that cancers arising from this seeding appear to be rare.
An enumeration of small percentagesĚý
Contrary to the caricature of sociopathic doctors painted in some corners of the wellness scene, medical professionals have been concerned with needle tract seeding for a while. The first cited report of this phenomenon was publishedĚý. It involved a 70-year-old man diagnosed with prostate cancer. Following the removal of his prostate, he developed cancer in the tissue underneath the skin that had been traversed by the biopsy needle. The doctors at the time wrote, “That such a complication may occur makes caution necessary in the selection of patients for this diagnostic procedure.”
Basically, needle tract seeding is not a secret. There are, in fact, dozens and dozens of studies trying to nail down how frequent it is—what we call its incidence.
It’s impossible to boil it down to a single number, however. It varies from one type of cancer to another. Some of the studies were done on so few biopsies that the number reported is likely to be biased in an important way. One suchĚýĚýreported that 25%—one in four—of a specific type of breast cancer biopsy (known as a multiple-puncture biopsy) led to seeding. But the authors only looked at eight biopsies, finding seeding in two of them. InĚýĚýof over 63,000 fine needle aspirations done for a wide range of possible cancers, only three needle tract seedings were reported.
Needle tract seeding, it seems to me, has received the most research attention when it comes to diagnosing hepatocellular carcinoma. The cancer, known as HCC for short, is the most common form of liver cancer, and multiple studies have attempted to see just how frequent needle tract seeding is when doctors biopsy the liver and it turns out to be HCC. AĚýĚýlists the various incidences that have been reported. Outside of an abnormally high outlier, 2.7%, the numbers are low: 0.13% in one study, a range of 0.003 to 0.009% in one meta-analysis, and 0% in a sample of 128 biopsies. An added difficulty when studying this complication is that it can be difficult to distinguish between two scenarios: the biopsy needleĚýł¦˛ąłÜ˛ő±đ»ĺĚýa new cancer to sprout near the original tumour… and the original cancer simply recurred and thus a new cancer sprouted near the original tumour. Blaming the needle is not simple. A recentĚýĚýfor HCC put the incidence of needle tract seeding at 0.62% (meaning 31 cases per 5,000 biopsies) and showed that that number was lower than it had been in the 1990s, presumably because of improved technique.
What’s interesting is that seeding is not enough for cancer to arise. The mere presence of these cells along the tract the needle took is not enough. Our immune system often kills them off, while others are eradicated by the cancer treatments themselves.
Weighing risks and benefits
There are potential, and hotly debated, risk factors for tumour seeding. It is thought that the bigger the needle, the higher the risk (although the evidence is mixed), and that the more “passes” are done—each pass being a needle going in, getting a sample, and being pulled out—the more likely tumour cells will be left along the tract. Likewise, tumours that, because of their biology, are eager to spread are thought to increase the chances of tumour seeding during a biopsy.
There’s always room for improvement when it comes to doctors diligently and clearly explaining the risk of a procedure to a patient. And when it comes to needle tract seeding, more research is needed, as the studies conducted on this topic are not always of high quality and its incidence may be underestimated. But doctors have and continue to take this potential consequence of biopsies seriously.
Many physicians advocate forĚý°ů±đłľ´Ç±ąľ±˛Ô˛µĚýthe tissue that came into contact with the biopsy needle when the patient undergoes surgery to have the cancer itself cut out. Another common suggestion is to keep the number of biopsy passes to a minimum. Also, depending on the context, a biopsy may not be the only, or the best, diagnostic tool to use. Imagery may be preferred.Ěý
Over the years, a number of experimental ways have been devised to reduce the likelihood of tumour seeding, from leavingĚýĚýfull of a chemotherapeutic drug to dissolve in the path of the needle to using a vacuum or evenĚýĚýto destroy any cancer cells left in its wake. Doctors are actively trying to keep the risk as low as possible.
The human mind struggles to evaluate risk. Our near-allergy to numbers may be partly to blame. While some influencers loudly proclaim the alleged danger of a biopsy when a cancer is suspected, others line up to get a full-body MRI scan in the absence of symptoms, even thoughĚýĚýby this procedure when no disease is expected. Medicine is all about ensuring the benefits of a procedure outweigh its risks. Needle tract seeding is not a negligible risk, but as far as we know, the chances of it happening are quite low. Doctors should always ask themselves if a less invasive method is available; but if it isn’t, the knowledge gained from a biopsy has to beĚýheavily weighedĚýagainst the very low risk of tumour seeding.
In an article on how the risk of needle tract seeding can be reduced, breast surgeon Dennis Holmes wrote that some women concerned with this possible complication are deferring the biopsy by weeks, if not months. As he points out, aĚýĚýbased on clinical data has shown that a delay of three months or more between a concerning finding during a mammography and receiving a diagnosis of breast cancer via biopsy—the kind of delay that can be due to the exaggerated concern that a biopsy will simply spread the cancer further if it’s there—reduces a woman’s chances of surviving byĚý20%. Why? Because cancers grow over time, and delays feed a tumour.
And that’s the poisonous irony at the centre of the malignant discourse over biopsy consequences. In trying to avoid a low risk, people give in to a much larger, much more certain risk that can shave years off of their lives, if not decades.
Take-home message:
- Needle tract seeding is the rare complication where the needle biopsy of a cancerous tumour leaves a trail of cancer cells in its wake, and these cancer cells can then form a new tumour.
- The benefits of a biopsy when cancer is suspected usually far outweigh this risk, and doctors are typically told to minimize the number of passes, use a vacuum-assisted device, or instead use medical imagery to keep the risk to a minimum.
