The short answer
What a biopsy is, the main types, what to expect afterwards, how to prepare, and why ACS says cancer spread after a biopsy is extremely rare.
ACS says a biopsy is the only way to know for sure if an abnormal area is cancer. Imaging cannot see cells.
Fine needle aspiration uses a thin needle to collect cells. Core needle biopsy uses a larger hollow needle to remove pieces of tissue.
With a local anesthetic, the area is numbed so you should not feel pain, but you may feel pressure.
Needle tract seeding is real but rare. ACS cites a 2015 review with an incidence under 1%, and a 2008 review with 2.7% in liver cancer biopsies.
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What a biopsy is for
A biopsy takes a sample of tissue so a pathologist can look at the cells under a microscope. ACS says a biopsy is the only way to know for sure if an abnormal area is cancer. Scans show shape and size. They cannot see cells. Ask your doctor why they recommend a specific type of biopsy for you.
The main types
A sample may be taken with a needle, through a small cut during an endoscopy, or during surgery. ACS says different types of sedation and anesthesia might be used, depending on the test.
Fine needle aspiration uses a thin needle to collect a small sample of cells or fluid.
Core needle biopsy uses a larger hollow needle to remove pieces of tissue.
Surgical biopsies remove all or part of a lump.
Bone marrow biopsy and aspiration collect marrow. ACS says the aspiration uses a smaller needle and is done first. The biopsy uses a larger needle. Most often they are done on the hip bone.
Sentinel lymph node biopsy is a way to find out if cancer has spread to nearby lymph nodes.
What it may feel like
For a needle biopsy, your provider cleans the skin and usually numbs the area with a shot of medicine. MedlinePlus says you may feel a little pressure when the sample is removed.
Bone marrow biopsies can be painful. ACS says the pain differs from person to person. Many people describe the aspiration as sharp but short-lived. The biopsy is often duller. ACS says some providers give medicine before the procedure for pain or anxiety. Local anesthesia numbs the skin but does not make you sleepy.
Afterward, MedlinePlus says some bruising and temporary discomfort are common after a breast biopsy. Bleeding and infection are the recognized risks of a biopsy. Your provider will tell you how to care for the site and manage discomfort.
The myth that biopsies spread cancer
This belief is widespread. People may delay or decline biopsies because of it.
ACS says cancer spread after a biopsy can technically happen, but it is extremely rare. It is called tumor seeding or needle tract seeding. ACS gives these examples:
- A 2008 review found needle tract seeding in 2.7% of liver cancer biopsies.
- A 2015 review of studies found the incidence of seeding was under 1%.
- A 2019 study followed 42 people with bladder cancer who had a core needle biopsy. No seeding was found after 28 months.
- A 2024 review found that a needle biopsy of the breast does not significantly affect the chance of breast cancer coming back, spreading, or overall survival.
ACS quotes an expert from ASCO. Ask your doctor why they recommend the biopsy. Ask what the risks are of having it and of not having it.
Practical preparation
Ask whether you need to stop blood thinners, including aspirin, and how far in advance. ACS says you may be asked to stop them for several days before a bone marrow biopsy. Ask whether you will be sedated, and whether you need someone to take you home. Ask how many samples are planned and how long results usually take. If you are anxious, say so before the procedure. ACS says medicine can be given for anxiety or pain.
When to get help sooner
- Call 911 or go to an emergency department if you cannot stop bleeding from the site with firm pressure, or if after a lung, liver or kidney biopsy you get sudden chest pain, sharp breathlessness, or you cough up blood. Do not drive yourself. Also go if you are suddenly confused or hard to wake.
- Call your care team right away if your temperature reaches 100.4°F (38°C) or higher, or the site turns hot, red and swollen or starts leaking fluid. MedlinePlus lists infection and bleeding as the recognized risks of a biopsy. If you are having chemotherapy or have low white blood cells, call day or night. Chills, a sore throat, or any other sign of infection also mean call right away. A normal temperature is not permission to wait.
- Call your care team the same day if soreness is getting worse instead of easing, bruising keeps spreading, or a small ooze from the site keeps restarting.
Your own clinic's instruction sheet takes priority over this list, because it is written for the exact biopsy you had.
Sources
Common questions
Can a biopsy make cancer spread?
ACS says spread after a biopsy can technically happen, but it is extremely rare. It is called needle tract seeding. ACS cites a 2008 review with seeding in 2.7% of liver cancer biopsies, and a 2015 review that found under 1%. A 2019 study of 42 people with bladder cancer found no seeding after 28 months. A 2024 review found breast needle biopsies did not significantly affect the chance of breast cancer coming back or spreading.
Will it hurt?
For a needle biopsy, your provider usually numbs the area with a shot of medicine so you should not feel pain. MedlinePlus says you may feel some pressure. Bone marrow biopsies can be painful. ACS says the aspiration is often sharp but short-lived, and the biopsy is often duller. Tell your team if you are anxious. ACS says medicine can be given before the procedure for pain or anxiety.
How many samples will they take?
It depends on the biopsy. Ask your team how many samples are planned and how long results will take. MedlinePlus says breast biopsy results may take several days to a week.
What should I expect afterwards?
MedlinePlus says some bruising and temporary discomfort are common after a breast biopsy. Bleeding and infection are the recognized risks of a biopsy. Your provider will give you instructions on caring for the site and managing discomfort. Follow them. Call your care team about bleeding, fever, or worsening pain.
Do I need to stop my medications?
Ask specifically about blood thinners, including aspirin. ACS says you may be asked to stop them for several days before a bone marrow biopsy to reduce bleeding risk. Also ask whether you will be sedated, since that decides whether you need someone to take you home.
Questions to ask your doctor
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Written by: Cancer ExplainedSources last checked: 2026-08-13 what this meansLast updated: 2026-09-29Next planned review: 2027-07-30
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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