Surgery to the lymph nodes for breast cancer

There are different types of lymph node surgery. Your surgeon may remove some or all the lymph nodes in your armpit to check them for invasive cancer cells.

What is surgery to the lymph nodes?

Your surgeon may remove some or all the lymph nodes in your armpit to check for cancer cells. This can:

  • remove any lymph nodes that contain cancer cells – but you may need more treatment to the armpit if only some lymph nodes were removed
  • gives information about the stage of the cancer – this helps when making decision about having other treatments.

There are different ways some or all the lymph nodes may be removed:

  • a test called a sentinel lymph node biopsy (SNLB) that removes 1 to 3 lymph nodes for testing
  • an operation to remove all the lymph nodes under the arm that is called an axillary lymph node dissection.

If you have DCIS you only have a SLNB if you are having a mastectomy. They are done at the same time.

With invasive breast cancer you have an SLNB when the ultrasound of the lymph nodes or fine needle aspiration are normal. If the SLNB shows cancer cells you usually need the remaining lymph nodes in the armpit removed or treated.

Some people have all the lymph nodes from the armpit are removed. This is called an axillary lymph node dissection. You usually have this when tests on the lymph nodes or an SLNB show there are cancer cells in the lymph nodes or there is a high risk of this.

Sentinel lymph node biopsy (SLNB)

A sentinel lymph node biopsy (SLNB) is a way of checking the lymph nodes in the armpit. The lymph nodes most likely to have cancer cells in them are the sentinel lymph nodes. These are the first nodes that lymph fluid drains to from the breast.

Having a sentinel lymph node biopsy at the same time as a mastectomy means you do not need a second operation to check the lymph nodes. Women having breast conserving surgery do not usually have an SLNB.

During an SLNB, surgeons remove the smallest number of lymph nodes possible (usually 1 to 3) to see if they contain cancer cells. Removing only a small number of lymph nodes reduces the risk of side effects of lymph node surgery. These include swelling of the arm (called lymphoedema) and stiffness of the arm and shoulder.

If there are no cancer cells in the sentinel nodes, you will not need any further treatment to the lymph nodes.

If cancer cells are found in the sentinel lymph nodes, your cancer doctor will talk to you about whether you need further treatment. You may be offered another operation to remove the remaining lymph nodes. Some people have radiotherapy to the rest of the lymph nodes instead of more surgery.

In some hospitals, the sentinel lymph nodes can be checked for cancer cells during your operation to remove the cancer. This means that if more lymph nodes need to be removed, it can be done during the same operation.

How an SLNB is done

Before the sentinel lymph nodes can be removed, the surgeon needs to check which nodes are the sentinel lymph nodes.

Before the surgery, the surgeon injects a harmless amount of radioactive liquid into your breast. During the operation, they use a handheld machine to find the lymph nodes that have picked up the radioactive liquid. The surgeon may also inject a blue dye into your breast during the operation. This stains the sentinel lymph nodes blue. The lymph nodes that pick up the radioactive liquid or become blue first are the sentinel lymph nodes.

The surgeon can then remove the blue or radioactive nodes (sentinel nodes). These are tested to see if there are any cancer cells in them.

Removing all the lymph nodes

If you have invasive breast cancer, the surgeon will sometimes recommend removing all the lymph nodes in the armpit. This is called an axillary lymph node dissection (ALND) or clearance.

An ALND is usually done when there are cancer cells in the fine needle aspiration (FNA) or biopsy of the lymph nodes.

There is an increased risk of developing swelling of the arm called lymphoedema after having an ALND.

About our information

  • References

    Below is a sample of the sources used in our breast cancer information. If you would like more information about the sources we use, please contact us at

    European Society for Medical Oncology. Primary breast cancer: ESMO clinical practice guidelines for diagnosis, treatment and follow-up. Annals of oncology 26 (supplement 5): v8–v30. 2015.

    Morrow M, et al. Chapter 79: malignant tumors of the breast. DeVita, Hellman and Rosenberg’s cancer: principals and practice of oncology (10th edition). Lippincott Williams and Wilkins. 2014.

    National Institute for Health and Care Excellence (NICE). Early and locally advanced breast cancer: diagnosis and management. July 2018.

    Scottish Intercollegiate Guidelines Network. SIGN 134. Treatment of primary breast cancer: a national clinical guideline. September 2013.

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Rebecca Roylance, Consultant Medical Oncologist.

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