Ultrasound-guided core biopsy of the breast

This information is about having an ultrasound-guided core biopsy of the breast.  

A core biopsy is a procedure where we remove a small sample of tissue from the breast. The sample can then be examined under a microscope. We use an ultrasound machine to:

  • find the area of the breast that needs to be examined
  • guide the biopsy needle to the correct position

A specialist health professional called a radiologist or an advanced practitioner mammographer does your core biopsy in our breast imaging unit

The aim of this information is to help answer some of your questions about having a core biopsy. It explains:

If you have any more questions or concerns, please speak to a radiologist or an advanced practitioner mammographer in the breast imaging unit or a breast care nurse.

Benefits of a core biopsy

If a mammogram (X-ray of the breasts) or ultrasound scan shows changes in your breasts, we need to find the cause.

We take a sample of cells (a fine needle aspiration) or tissue (a biopsy). The sample can then be checked under a microscope and the results can help us to make a diagnosis.

Risks of a core biopsy

Sometimes, there might be some bleeding inside the breast after a biopsy and you get a bruise or swelling. This is called a haematoma. 

During the procedure, we try to reduce the risk of infection. We also take care not to pass the needle beyond the breast through the chest wall. This is especially important if you have a lump at the back of a small breast.

Other treatment options

Another possible test that we might offer you is called a diagnostic excision biopsy. You have the procedure in the operating theatre under a general anaesthetic. A general anaesthetic is a medicine that makes you sleep during the procedure and stops you feeling pain.

A diagnostic excision biopsy is surgery to remove a lump or suspicious area from the breast. The surgeon also removes a small surrounding area of normal tissue called a margin.

The procedure leaves a scar and the recovery time is longer.

Preparing for a core biopsy

There are no special preparations for having a core biopsy. You can eat and drink as usual before and after the procedure.

Before having a core biopsy, you need to tell us if you take:

You might need to stop taking these medicines for a short time before the procedure. Please tell the radiologist or advanced practitioner mammographer before the procedure starts, or call the breast care nurses for advice when you get your appointment letter.

We need to know if you are allergic to any medicines, particularly local anaesthetic used to make the breast area numb. When you get your appointment, please contact us as soon as possible if you have any allergies to medicines.

There are also some things that can make your core biopsy appointment easier.

Tips for your core biopsy appointment


  • Contact the breast imaging unit in advance if you need a hoist (piece of medical equipment to help lift or move you safely), transport or a translator.
  • Wear clothes that you can remove easily. This is because we ask you to undress from the waist upwards.
  • Try to bring a family member or friend with you to your  appointment. This may also be useful if you do not understand English well or have any special needs. Although your family member or friend may not be allowed into the examination room, they can support you and accompany you home.
  • Bring an adult to supervise your children if they need to come with you to your appointment. We do not have childcare facilities.
  • If you wish, tell staff the pronouns (such as he or him, she or her, or they or them) that we should use to address you.


  • Do not wear spray deodorant (roll-on deodorant is OK), powder, lotion or perfume on your breasts and underarm areas on the day of your appointment. These products can affect the accuracy of your results.

Preparing for a core biopsy if you are trans or non-binary

If you have any questions or concerns about coming for a core biopsy, you can:

You may want to bring someone with you to your appointment for support.

It is important that you feel treated with respect and dignity at all times. When booking your appointment, please tell us if you would prefer to be seen at the beginning or end of a clinic.

We may ask you to sit in a waiting area when you arrive for your appointment. Please tell our staff if you do not feel comfortable waiting with other people.

Before your core biopsy, you get undressed from the waist upwards behind a curtain in the ultrasound room. We give you paper to cover your top half and then move this to uncover the breast during the ultrasound scan.

If you wear a binder (a piece of clothing to flatten breast tissue), you will need to remove this before the procedure.

We want to involve you in decisions about your care and treatment. If you decide to have a core biopsy, we will ask you to sign a consent form. This says that you understand what is involved and agree to have the test.

You can read more about our consent process.

Having the procedure

The procedure should last no longer than 20 minutes and is done in an ultrasound room. Please allow extra time in case there are any delays on the day of your appointment. You might also want to take time to rest and recover after the procedure.

What happens during the procedure

  1. You remove all of your clothes from the waist upwards behind a curtain in the ultrasound room. We give you paper to cover your top half and move this to uncover the breast during the ultrasound scan.
  2. We ask you to lie on a couch. You put your arm on the affected side above your head on a pillow.
  3. The radiologist or advanced practitioner mammographer cleans the area of the breast that will be examined. They inject a medicine called a local anaesthetic into this area to make it numb and free from pain.
  4. When the area is numb, the radiologist or advanced practitioner mammographer makes a very small cut that is 3 to 4mm long. They can then gently put the biopsy needle into the breast. The ultrasound machine is used to guide the needle into the correct position.
  5. The radiographer or advanced practitioner mammographer passes the biopsy needle, which has a spring, quickly into the breast. You might hear the needle make a clicking noise. They then take a small sample of breast tissue and remove the needle. This process may be repeated 2 to 4 times.
  6. When we have taken enough samples and the procedure is finished, a member of staff puts pressure on your breast for 5 minutes. This helps to reduce the risk of bleeding or bruising.
  7. We put a paper stitch called a Steri-Strip™ over the site and cover it with a sterile, waterproof dressing. You need to wear this dressing for 3 days. On the 4th day, you can remove the dressing and Steri-Strip.
  8. After we have covered the site, you can get dressed. A quiet room is available in the department if you need some time to rest after the procedure.

How the procedure feels

During the procedure, the local anaesthetic may cause some stinging before it makes your breast numb. This should only last for a few seconds.

You may feel some pressure on the breast during the procedure, but this is not usually painful. If you do feel any pain, please tell the radiologist or advanced practitioner mammographer. They will then use more local anaesthetic.

When the local anaesthetic wears off after 2 to 3 hours, your breast may be tender or painful. If the area becomes particularly uncomfortable, you can take a mild painkiller like paracetamol. You can buy this medicine from a pharmacy or shop and follow the instructions on the pack.

It is best to avoid taking:

These medicines could cause bruising in the breast.

After the procedure

You can return to your usual activities immediately. However, it is best to avoid any activities that involve a lot of effort or energy for the rest of day. Examples are heavy lifting, jogging or aerobics.

If your work is physical, we recommend that you do light duties only for the rest of the day. You can then continue your usual duties the next day.

If you take any medicines that prevent blood clots or thin the blood, you might need to stop them for a short time after the procedure. The radiologist or advanced practitioner mammographer talks to you about this before you go home. Please call our breast care nurses if you have any questions about your medicines after the procedure.

You can take any other usual medicines as prescribed, unless we give you different advice.

You keep the dressing on your breast for 3 days. After this, you can remove it and do not need any more dressings.

While wearing the dressing, you can have a shower or bath as normal because it is waterproof. We give you an aftercare sheet with more information.

What to do if you have a problem

You might notice some bruising at the site where we took a sample of breast tissue. This is to be expected after a core biopsy and the bruising should reduce within the next 7 to 10 days.

Bleeding or swelling is rare but, if it does happen, please follow these instructions:

  1. Remove the dressing from your breast.
  2. Put pressure on the area where we took the sample, just like a member of staff did immediately after the biopsy. Do this firmly by pressing with the palm of your hand for 10 minutes using tissues or a paper kitchen towel.

Go to your nearest A&E or minor injuries unit if:

the bleeding or swelling continues after 15 minutes

Getting your core biopsy results

After the procedure, we send the samples of breast tissue to be checked in a laboratory. We usually get your results within 1 week.

You may have come for your core biopsy as part of an appointment at the breast unit one stop clinic. If so, you will get your results by post or we may ask you to return here after all your tests have been done. The breast consultant can then tell you when you should expect to get your results.

If you have come for an outpatient appointment, your consultant will give you the results at your next appointment. Please make sure that an appointment is arranged for you to get your results and talk about them with your consultant.

Resource number: 3322/VER6
Last reviewed: January 2024
Next review due: January 2027

A list of sources is available on request.

Trusted Information Creator. Patient Information Forum

Contact us

Please contact us if you have any questions.


  • For your breast imaging appointment: 020 7188 8317, Monday to Friday, 9am to 5pm
  • For outpatient clinic appointment bookings: 020 7188 0881 or 020 7188 7188, extension 53480, Monday to Friday, 9am to 5pm
  • For your results, contact the breast unit secretaries: 020 7188 1469, Monday to Friday, 9am to 5pm
  • For the breast care nurses: 020 7188 0869, Monday to Friday, 9am to 5pm

If you have a serious medical problem out of hours, contact a GP. In an emergency, call 999 for an ambulance.


Breast imaging unit: [email protected]

We aim to respond to emails within 2 working days.


Breast imaging unit, 3rd floor, Tower Wing, Guy's Hospital, Great Maze Pond, London SE1 9RT

Pharmacy medicines helpline

If you have any questions or concerns about your medicines, please speak to the staff caring for you.

You can also contact our pharmacy medicines helpline.

Phone: 020 7188 8748, Monday to Friday, 9am to 5pm

Email: [email protected]

We aim to respond to emails within 2 working days.

Do you have any comments or concerns about your care?

Contact our Patient Advice and Liaison Service (PALS)

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