Breast cancer cells can sometimes spread to the lymph nodes under the arm.

Anyone with invasive breast cancer will have the lymph nodes under the arm assessed. The outcome of this will help the specialist team recommend which treatments are best for you.     

The lymph nodes

Breasts contain a network of tiny tubes called lymph vessels. These are connected to the lymph nodes (glands) under the arm.

Lymph nodes are arranged in three levels, and the exact number of nodes in each level varies from person to person.

lymph nodes diagram

The above is a basic illustration of the different levels of lymph nodes. Where the lymph nodes are situated and how many lymph nodes you have will vary according to each person.

Checking lymph nodes before surgery

If you have invasive breast cancer, your specialist team will want to check if any of the lymph nodes under the arm contain cancer cells. This helps them decide whether you’ll benefit from additional treatment after surgery.

Usually an ultrasound scan of the underarm (known as the axilla) is done before surgery to assess the lymph nodes.

If this appears abnormal, you’ll have a fine needle aspiration (FNA) or a core biopsy to see if the cancer has spread to the lymph nodes. An FNA uses a fine needle and syringe to take a sample of cells to be looked at under a microscope. A core biopsy uses a hollow needle to take a sample of tissue for analysis under a microscope.

Lymph node removal

If the FNA or core biopsy shows cancer has spread to the lymph nodes you’ll usually be recommended to have all or most of your lymph nodes removed at the same time as your breast surgery. This is known as an axillary clearance.

Sentinel lymph node biopsy

If the tests before surgery show no evidence of the lymph nodes containing cancer cells, you usually still need to have a sample of the lymph nodes removed to confirm this. This is known as axillary sampling.

Sentinel lymph node biopsy is widely used for axillary sampling. It identifies whether or not the first, or sentinel, lymph node (or nodes) is clear of cancer cells. The sentinel node is usually in level 1.

Before your breast cancer surgery, your doctor will inject a small amount of radioactive liquid into the breast, close to the cancer. This may be done just before your operation or the day before.

During the operation, your surgeon injects a small amount of blue dye into the breast. The radioactive liquid and the dye drain away from the breast tissue into the lymph node(s) closest to the area. The sentinel node(s) is then removed and examined under a microscope to see if it contains any cancer cells.

As the dye leaves your body, you may notice your urine is a bluish-green colour for one or two days after the procedure. The skin around the biopsy site may also be stained a blue-green colour. Some people may have a reaction to the dye but this is rare.

If the sentinel node(s) does not contain cancer cells, this usually means the other nodes are clear too, so no more will need to be removed.

If the results show there are cancer cells in the sentinel node(s) you may be recommended to have further surgery or radiotherapy to the remaining lymph nodes. 

If you’re having chemotherapy before your surgery, your specialist may want you to have a sentinel lymph node biopsy before starting chemotherapy. This can help with planning any further treatment to the underarm after chemotherapy.

Isolated tumour cells (ITCs), micrometastases and macrometastases

Your doctor may use one of these terms when discussing your sentinel lymph node biopsy result.

  • ITCs are single cancer cells or small clusters of cells no bigger than 0.2mm.
  • Micrometastases are cancer cells larger than 0.2mm but not bigger than 2mm
  • Macrometastases are cancer cells larger than 2mm.

If you’re diagnosed with ITCs or micrometastases, you will not usually need any further treatment to your axilla (under the arm).

If you have one or two sentinel nodes with macrometastases, you may or may not need further treatment to your axilla. This will depend on several factors including other characteristics of the cancer, for example what the grade is and whether you’re having hormone therapy. Your doctors may talk about going into a clinical trial that is comparing treating versus not treating the axilla.

If you have three or more sentinel nodes with macrometastases, you will need further treatment to the axilla.

Assessing lymph nodes during surgery

Some hospitals have the facility to assess the lymph nodes during breast surgery. The removed nodes will be looked at by a pathologist, who will tell the surgeon the result during the operation.

If the sentinel node(s) contains cancer cells, the surgeon will then remove more or all of the lymph nodes. Having lymph nodes assessed during surgery avoids a second operation. The most common test used is called One Step Nucleic Acid Amplification (OSNA).

Last reviewed: August 2016
Next planned review begins 2018

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