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Sentinel node biopsy

5-minute read

What is breast cancer?

Breast cancer is a harmful growth that starts in the glandular tissue of your breast.

What is a lymph node?

Lymph nodes are small structures which lie along lymph vessels present throughout the body.

Sentinel nodes are the first lymph nodes in your armpit to which breast cancer cells may spread. A sentinel node biopsy involves removing the sentinel nodes from your armpit.

What are the benefits of surgery?

The lymph nodes that your surgeon removes will be examined to see whether they contain cancer. The result will help to decide on further treatment, without needing to remove all of the lymph nodes from your armpit.

An illustration showing sentinal node biopsy.
The dotted lines show examples of where your surgeon may make cuts.
1. Lymph nodes and lymphatics (tubes for lymph) to breast and arm (green).
2. Sentinel lymph nodes in the armpit (stained blue from dye injection for surgery).

Are there alternatives to a sentinel lymph node biopsy?

Your breast cancer team may offer surgery to remove all the lymph nodes under the arm (axillary node clearance) if they have cancer in them.

Your breast cancer team may offer surgery to remove a sample of the lymph nodes from your armpit (axillary node sampling).

What does the operation involve?

You may be asked to come to hospital before your operation for an injection into your breast. The injection contains a fluid (tracer) which travels to the sentinel nodes and becomes trapped there.

The operation is performed under a general anaesthetic and usually takes 20 to 30 minutes.

During the operation your surgeon may inject a blue dye into your breast. The dye travels to the sentinel node and stains it blue.

A cut is made in your armpit, below the area where hair grows.

Your surgeon will remove the nodes identified using the blue dye or tracer.

The lymph nodes that your surgeon removes will be examined under a microscope. Your surgeon will know the results 2 to 4 weeks later.

If cancer cells are found in the sentinel nodes it means the cancer may have spread to other lymph nodes in your armpit. Your breast cancer team may recommend further treatment to the armpit, depending on how many of the sentinel nodes contain cancer.

What complications can happen?

Some complications can be serious and can even cause death.

General complications of any operation

  • infection of the surgical site (wound)
  • allergic reaction to the equipment, materials or medication
  • venous thromboembolism (VTE)

Specific complications of this operation

  • bleeding
  • developing a lump under your wound caused by fluid collecting
  • developing a lump under your wound caused by blood collecting
  • numbness or continued pain around your armpit or the inner part of your arm
  • swelling of your arm, hand or breast
  • allergic reaction to the tracer
  • discolouration of the urine, stools and tears for 1 to 2 days
  • sentinel node not found
  • failure to find cancer cells

Consequences of this procedure

  • pain
  • scarring of your skin

How soon will I recover?

You should be able to go home the same day or the day after.

You should be able to return to normal activities after 2 to 3 weeks.

Regular exercise should help you to return to normal activities as soon as possible. Before you start exercising, ask your breast cancer team or your GP for advice.

Your breast cancer team will arrange an appointment for you after surgery. The lymph nodes and any breast tissue that your surgeon removed will have been examined under a microscope. Your surgeon will tell you the results and discuss with you any treatment or follow-up you need. They will also check your wound and be able to tell you when you can return to work.


Sentinel nodes are the first lymph nodes in the armpit to which breast cancer cells can spread. A biopsy to remove the sentinel nodes gives your breast cancer team important information to help plan your future breast cancer treatment.


The operation and treatment information on this page is published under license by Healthdirect Australia from EIDO Healthcare Australia and is protected by copyright laws. Other than for your personal, non-commercial use, you may not copy, print out, download or otherwise reproduce any of the information. The information should not replace advice that your relevant health professional would give you. Medical Illustration Copyright ©

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Last reviewed: September 2023

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