Most biopsies won’t spread cancer. For cancers like testicular cancer, a biopsy can spread cancer, which is why physicians will remove suspected cancer rather than biopsy.
Biopsies have come under fire on social media recently. People are saying that biopsies aren’t safe because they can “seed” the cancer. Seeding is the term used for cancer spreading due to a biopsy. There’s a lot of nuance to this topic! For most cancers, there is an agreement within the medical community that there is an extremely low risk of a biopsy seeding cancer. There is a much higher risk of death if the cancer isn’t caught and treated. But, there are some cancers that aren’t biopsied because of the high possibility of seeding. For example, if someone is suspected to have testicular cancer, a physician will remove the suspected cancer rather than biopsy.
But let’s back up for a minute! We’ll start with talking about all of the different types of biopsies and then dive into the research around seeding.
What is a biopsy?
A biopsy is a technique that allows us to look at a bunch of cells that we take from an area of concern and determine if those cells could be cancerous. Doctors called pathologists look at the sample under the microscope to see what the cells look like. How the cell looks gives us a lot of information about whether or not something could be cancerous and if it is cancerous, how best to treat it.
Biopsies can be done wherever there might be cancer. For example, a skin biopsy for skin cancer, a cervical biopsy (called colposcopy) for cervical cancer, and a bone marrow biopsy, just to name a few. There are also a bunch of different methods for biopsies depending on the area that is getting biopsied. For example, a needle biopsy, which is often used in places that can be felt under the skin, can include a:
- Fine needle biopsy, which is a thin needle that allows clinicians to pull out a sample of cells.
- Core needle biopsy is similar to fine needle biopsy, but the needle is wider so that more tissue can be sampled.
- Vacuum-assisted biopsy involves a probe with a small rotating knife that is connected to a vacuum device. The vacuum device allows for the sample to be pulled out of the area once cut.
- Image-guided biopsy- this one is pretty special because it can be used for areas just under the skin, like a breast biopsy, or can be done by doctors called interventional radiologists, who use scans like CT scans to figure out where to biopsy.
Skin biopsies for concerning bumps or lumps can include:
- Shave biopsies, which take a tiny piece off the surface of the skin.
- Punch biopsies, which is basically a hole-punch that allows physicians to look at multiple layers of the skin.
- Excisional biopsies, which is when the entire area of concern on the skin is removed.
And then there are biopsies that occur for organs, where a scope (a camera) is passed into the throat or anus to look at the area generally. Then a biopsy can be taken from those areas. Sometimes, a biopsy won’t be taken during the procedure (for example, if the clinician doesn’t see any area of concern). But biopsies are often taken during these procedures. Examples of scoping with biopsies can include:
- Cystoscopy, which allows a clinician to sample cells from the bladder
- Colonoscopy, which looks at the colon generally and allows a clinician to take biopsies of any polyps.
- Bronchoscopy, which allows a clinician to take lung samples to check for lung cancer.
What about the risks people talk about on social media?
First, let’s talk about risks/benefits for procedures generally. If you’ve ever had a procedure, you might remember your clinician going over a consent form with you. The consent form details the risks of the procedure. For example, if you’re having surgery, there is a risk you can bleed, and there is a risk of injury to any internal organs in the area where you’re getting surgery. All procedures carry risk. But another part of the consent form will talk about the risk of *not* doing the procedure.
In the case of cancer, the risk of *not* doing the biopsy can be that we miss a very bad cancer and it spreads. And the benefit is that if we catch the cancer early, we can proceed with the best treatment faster. With some types of cancer time is of the essence. Is there a small risk that getting a biopsy could possibly unsettle the cells and spread the cancer? Yes. But most of the data suggests it’s not common. And when it does happen, it’s often clinically more important to know that it is cancer, and what type it is, so it can be treated appropriately.
Since there are a lot of different types of cancer and a lot of different biopsies, there is a lot of research about the safety of biopsies. So let’s look at some of this research!
Pancreatic Cancer
One study suggested seeding is a rare risk associated with certain types of ultrasound-guided pancreatic biopsies, but that it occurred in only 0.33% of patients. Another study suggested that ultrasound-guided fine needle aspiration of pancreatic tumors was not associated with an increased risk of death.
Nerd Alert: Whenever we look at clinical studies, we want to think about what the result is saying about morbidity or mortality. In other words, does a certain procedure or medication actually impact the health and lifespan of people in a positive or negative way? In the case above, ultrasound-guided fine needle aspiration, regardless of seeding, was not associated with an increased risk of dying.. Another example includes a medication that may reduce levels of bad fats in our blood, but if it does that and is not *also* decreasing the likelihood of death because of cardiovascular disease, then that medication is not leading to better outcomes for people and may not be worth taking.
Prostate Cancer
A literature review on prostate biopsies showed that the incidence of seeding was less than 1%. A small study showed that prostate needle biopsy didn’t result in tumor cells getting into the blood.
Breast Cancer
One study looked at seeding in certain types of breast cancer biopsies. They found that seeding happened in about 3% of the cases, but there wasn’t a difference in recurrence of the breast cancer in patients who had gotten a lumpectomy after their biopsy, regardless of seeding. A lumpectomy is when the lump of cancer is removed. Here, while there is a small risk for seeding, it didn’t impact clinical outcomes for the patients. We also know that for breast cancer, the longer the time between an abnormal screening, like a mammogram, and a diagnostic test like a biopsy or lumpectomy, the lower the rates of overall survival. So that’s where risk/benefit discussion should come in when you talk to your clinician.
Liver Cancer
A meta-analysis of biopsies for liver cancer showed that the overall risk for seeding was around 2.7%. 2.7% isn’t a very high risk and it’s also important to recognize that not treating liver cancer leads to a high risk of death.
Nerd Alert: A meta-analysis looks at a bunch of different studies to draw conclusions about a particular question.
Bladder Cancer
In a study looking at bladder cancer, no seeding was found after core-needle biopsy.
Some biopsies can seed cancer–so we don’t perform them
For some cancers, we don’t biopsy because their location makes it more likely for cancer cells to spread! For example, if someone has a lump in their testicle that is possibly cancer, a clinician will do an ultrasound to look at the makeup of the lump. Cancer tends to look different on ultrasound than other conditions. A clinician might also draw blood to check for different proteins, called “tumor markers,” which could further point in the direction of cancer. Then, based on that information, a urologist will perform a procedure called an orchiectomy, which is where the entire testicle is removed. The reason the urologist jumps straight from the ultrasound to removal is because a biopsy could spread the cancer into the lymphatic areas (the places where extra fluid is drained) of the scrotum. So we just don’t run that risk!
Bottom line: Biopsies can rarely seed cancer, but the risk of waiting for a biopsy that will help guide treatment for a cancer is greater than the risk of seeding. Biopsies can often be one of the only ways to confirm whether a concerning mass is cancer or not, and can sometimes help guide the best treatment, so they’re really important. If you are concerned about the possibility of tumor seeding in your situation, please discuss this with your clinician. They can explain the specific risks and benefits based on the location and type of biopsy recommended for you.
