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Magseed localisation

Read our guide below about magseed localisation.

You can also download a PDF version of this patient information by following the link on the right.

What is magseed localisation?

It’s a procedure to help a surgeon remove the correct piece of breast tissue during surgery.

Magseed is a tiny metallic seed (smaller than a grain of rice) that a radiologist or advanced practitioner inserts into the breast tissue by a radiologist. This is done under x-ray or ultrasound.

The procedure can be done any time before your surgery. You’ll need to come to the Breast Unit as an outpatient.

What does the procedure involve?

It’s like the core needle biopsy you’ll have had to your breast that confirmed your diagnosis.

The radiologist will place the magseed in the breast tissue using a local anaesthetic. They’ll then use a thin needle to place the seed into the area of the breast that needs removing.

You may feel some pressure in your breast during the procedure, but it’s normally painful. If you feel any pain, tell the staff so they can give you more local anaesthetic. You won’t be able to feel the seed once it’s inserted and you can continue with your normal activities.

You’ll have a small dressing over the puncture site.

The procedure will usually take about 30 minutes. You’ll then have a mammogram to confirm the site of the Magseed.

What are the risks of magseed localisation?

These include:

  • bruising and discomfort. If you have pain or discomfort you can take paracetamol. Never take aspirin or ibuprofen.
  • bleeding on the dressing*
  • infection – a high temperature and/or redness may indicate infection. Please contact your Breast Care Nurse.

* This is normal. Heavy bleeding that soaks through the dressing is very rare but if this happens apply firm pressure. If bleeding continues and you’re concerned, contact your Breast Care Nurse.

After care advice

You can:

  • remove the dressing after 24hrs
  • return to work and most activities the following day
  • shower the day after the procedure

You must not:

  • soak in a bath or go into a swimming pool for 48hrs
  • do any heavy lifting for 24 hrs.

We recommend that you wear a comfortable supportive undergarment for 24hours.

What happens during surgery?

While you’re asleep under general anaesthetic, the surgeon will use a highly sensitive magnetic detector to identify the seed and location of the breast tissue that needs
removing. The surgeon will then go ahead with your surgery and remove the seed at the same time.

What if I have any questions?

The Breast Care Nurses will be happy to answer any further questions or concerns. Please leave a message and they’ll return your call.

How can I help reduce healthcare associated infections?

Infection prevention and control is important to the wellbeing of our patients so we have procedures in place. Keeping your hands clean is an effective way of preventing the spread of infections.

You, and anyone visiting you, must use the hand sanitiser available at the entrance to every ward before coming in and after you leave. You may need to wash your hands at the sink using soap and water. Hand sanitisers are not suitable for dealing with patients who have symptoms of diarrhoea.

More help or advice

Contact our patient advice and liaison service (PALS) on 01296 316042 or

About our patient information

We aim to make the information as up to date and accurate as possible, but please note that it’s subject to change. You must always check specific advice on any concerns you may have with your doctor.

Contact us

Breast Care Nurses, Wycombe Hospital
Breast Care Nurses, Wycombe Hospital

01494 426228

Mondays to Fridays, 9am to 4.30pm.