Sentinel Lymph Node Biopsy

Patient Experience

  • Reference Number: HEY-017/2022
  • Departments: Breast Care, Breast Services, Oncology (Cancer Services)
  • Last Updated: 1 May 2022


This leaflet has been produced to give you general information about this procedure. Most of your questions should have been answered by this leaflet.  It is not intended to replace the discussion between you and your doctor/nurse but may act as a starting point for discussion. If after reading it you have any concerns or require further explanation, please discuss this with a member of the Macmillan Breast Care Nursing Team who has been caring for you.

Why am I being offered this procedure?

Part of the treatment for breast cancer involves removal of some or all of the lymph nodes under the armpit (axilla). The lymph nodes are examined to determine whether any cancer cells are present in them

What is a sentinel node?

The first lymph nodes that the breast drains into are called the sentinel nodes. Large national and international trials have shown that removal and assessment of these nodes is a reliable method of detecting cancer cells in the lymph nodes and is now standard practice. Some people may have more than one sentinel node and the surgeon will remove more than one if necessary.

How is surgery done?

An appointment will be made for you to attend the hospital on the day of your planned breast operation (if appropriate), or the day before if surgery is early in the day.

At least one hour before your surgery you will have a small amount of radio-active tracer injected into the area around the nipple. This is not generally painful, and the amount of radio activity is minimal.

Around 1–2 hours after this injection, you may have a scan, which will identify the first node that takes up the radioactive tracer.  This is a simple scan, which takes around 10 minutes and is similar to having an X-ray done. Note it is not always necessary to have a scan before your surgery and will not affect your treatment.

Whilst you are in theatre and under general anaesthetic, the surgeon will inject a blue dye into the breast area. This follows the route of the radioactive tracer and directs the surgeon to the sentinel nodes, which will be blue in colour. The surgeon will also check that the correct node has been removed by using a special probe to detect the levels of radioactivity in the node once it is removed.

Are there any side effects from the surgery?

You are not ‘’radioactive’’ following the injection of the radioactive tracer and the amount of radiation is less than the natural radioactivity you receive from the environment over a 3 month period.

The blue dye that is used is not known to be harmful, but some allergic reactions have been reported in less than 1% of patients. Most reactions usually occur whilst you are still in hospital and can be managed safely, should these occur.

In addition, you need to be aware of the following side effects that may occur which are normal:

  • Blue discolouration of urine and faeces for 24-72 hours
  • Blue staining around the injection site, which may persist up to one year

Will I have a scar?

Following your surgery you will have a small scar in your armpit, which will have dissolvable stitches and a small shower proof dressing or surgical glue.

This wound will be checked when you return to the breast clinic for the results of your surgery.

It is usual to expect some soreness and swelling around the scar.

Some patients describe a burning sensation or pins and needles on the inside of the upper arm, and you may experience some slight numbness on the inside of your upper arm. This is a normal side effect.

Most symptoms improve with time although there may be some residual long-term changes which your specialist will discuss with you.

It is important that you do the exercises given to you by your Macmillan Breast Care Nurse/ Clinic Nurse or the physiotherapist to ensure that your arm and shoulder movement is not restricted by this surgery.

Once your scar has healed it is important to regularly massage and moisturise your scar and surrounding area to reduce pain and tightness, flatten bulky scars to be softer and increase blood flow and hydration to the operated area. 


All patients having any surgery to their armpit are at increased risk of developing lymphoedema.

Lymphoedema is a swelling caused by a build-up of fluid in the tissues.

This condition is very rare following sentinel lymph node surgery. But it can occur weeks, months or years following surgery or radiotherapy treatment.

If you notice any swelling of the arm, hand, fingers, breast or chest wall, contact your Macmillan Breast Care Nurse or hospital specialist.

They will assess your symptoms and may want to investigate further as there may be other causes for the swelling.

You may also be referred to a lymphoedema specialist nursing team for advice and treatment to control and relieve the effects and impact on you.

If you would like further information about lymphoedema or to discuss your individual risk, please contact your Macmillan Breast Care Nurse. 

Also there is an information leaflet produced by Breast Cancer Now (2019) Reducing the risk of Lymphoedema if you would like any more information:

When will I receive the results of the surgery?

The sentinel node(s) will be examined by the histopathologist, to determine whether the node(s) contain cancer cells or not.

If the sentinel node(s) does contain evidence of cancer cells, you may be offered further surgery to remove the remaining glands, or possibly radiotherapy to the axilla. If the sentinel node(s) is clear of cancer cells, you will not require any further treatment to this area.

These results are usually available approximately 2 weeks after your operation; however, if you have also had breast surgery at the same time both these results are reviewed together by a team of specialists which may take an additional 2 weeks.

All of this information will be provided to you at your post-operative results appointment and explained to you by your surgical team.

Should you require further advice on the issues contained in this leaflet, please do not hesitate to contact the Macmillan Breast Care Nursing Team on telephone number: (01482) 622013

General Advice and Consent

Most of your questions should have been answered by this leaflet, but remember that this is only a starting point for discussion with the healthcare team.

Consent to treatment

Before any doctor, nurse or therapist examines or treats you, they must seek your consent or permission. In order to make a decision, you need to have information from health professionals about the treatment or investigation which is being offered to you. You should always ask them more questions if you do not understand or if you want more information.

The information you receive should be about your condition, the alternatives available to you, and whether it carries risks as well as the benefits. What is important is that your consent is genuine or valid. That means:

  • you must be able to give your consent
  • you must be given enough information to enable you to make a decision
  • you must be acting under your own free will and not under the strong influence of another person

Information about you

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We may pass on relevant information to other health organisations that provide you with care. All information is treated as strictly confidential and is not given to anyone who does not need it. If you have any concerns please ask your doctor, or the person caring for you.

Under the General Data Protection Regulation and the Data Protection Act 2018 we are responsible for maintaining the confidentiality of any information we hold about you. For further information visit the following page: Confidential Information about You.

If you or your carer needs information about your health and wellbeing and about your care and treatment in a different format, such as large print, braille or audio, due to disability, impairment or sensory loss, please advise a member of staff and this can be arranged.

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