Overview

A biopsy is when a sample of tissue is taken and looked at under a microscope. A sentinel lymph node (SLN) biopsy is a surgical procedure to remove one or more of the nodes (glands) from your armpit.

Lymph fluid from your breast drains to the sentinel node first, which means it’s the first place where cancer could spread. The nodes are examined under a microscope to see if they are cancerous.

The lymphatic system

The lymphatic system drains fluid from your body tissues. It plays an important part in keeping your blood clean and fighting infection. Breast cancer cells can spread through these channels. 

Each area of the body drains lymph fluid into nodes, usually the group of nodes that is closest. For the breast, the nearest group is usually in the armpit. The first node the fluid drains into is called the sentinel lymph node. Lymph nodes are like filters, they check what is passing through the body.

Patients who can have an SLN biopsy

In your original mammogram and ultrasound scans, we would have looked at your axillary lymph nodes. If any of these had signs of cancer, you may have had a biopsy with a fine needle to confirm the cancer cells.

If cancer was confirmed by this test, we will remove all of the axillary lymph nodes with cancer. This means that you won’t need an SLN biopsy.

You will need an SLN if the axillary lymph nodes showed no signs of cancer.

Giving your permission (consent)

We want to involve you in decisions about your care and treatment. If you decide to have the procedure or treatment, we will ask you to sign a consent form. This says that you understand what is involved and agree to have the treatment.

Read more about our consent process.

Before an SLN biopsy

Your appointment will be in the nuclear medicine department on the ground floor of Guy’s Cancer Centre.

You will have a small injection of a radioactive substance (tracer) into the skin of your breast. This helps to highlight the SLN. Although the word ‘radioactive’ might sound alarming, it is completely safe. 

During an SLN biopsy

The biopsy is done under general anaesthetic, which means you will be asleep and will not feel any pain. It is usually done at the same time as your breast surgery. There can be risks involved with having a general anaesthetic, but they are small.

An anaesthetist will see you before your surgery to make sure you are healthy enough for a general anaesthetic. Find out more about having a general anaesthetic.

The surgery

The surgeon will inject a blue dye under the skin around your nipple. A small cut is then made in your armpit. The dye and the radioactive tracer travel along your lymphatic channels to your sentinel nodes.

The surgeon uses a gamma probe device that finds radioactivity in the breast and armpit. This probe guides the surgeon to the nodes, and if they also appear blue in colour, the surgeon will remove them.

Benefits of an SLN biopsy

It’s important to find out if the cancer has spread to the lymph glands, so that your doctors can understand the stage of your breast cancer. It gives important information which is used to decide your treatment. 

Risks of an SLN biopsy

If you are worried about any of these risks, please talk to your breast team.

Infection

As with all surgeries, there can be a risk of infection. 

Pocket of fluid (seroma)

Sometimes a pocket of fluid will collect in the area of your biopsy. Symptoms of a seroma can be:

• swelling
• a feeling of fluid moving in the area
• discomfort

This usually settles down by itself after 4 to 6 weeks. In some cases, you might need to come back to the clinic to have it drained with a needle.

Stiffness or limited movement in the affected arm

It is common to feel this afterwards and it will improve as the wound heals. Your medical team will tell you how and when to move your arm. A physiotherapist will give you exercises to do too.

Discomfort

You might have some discomfort afterwards. This will improve as your wound heals. Your doctor will prescribe painkillers to help with this.

Numbness or tingling around the wound

This should return to normal as your body heals. If you are worried, please contact your breast care team.

Blue or green pee

As the dye is flushed from your body, you might notice a blue or green colour in your pee. This will last for 1 to 2 days and then return to normal.

Allergy

There is a small risk of an allergic reaction to the blue dye. Your surgeon will look for signs of allergy during your surgery. If you do have a reaction, you will be given medicine and be closely monitored.

Swelling (lymphoedema)

The affected arm can sometimes become swollen. A doctor or specialist nurse will diagnose this. There are lymphoedema specialist nurses who can help you manage and improve the symptoms of this. Please ask your breast care team to refer you to the lymphoedema specialist nurse, if needed.

Lymphoedema affects about 6 out of 100 patients who have an SLN biopsy procedure.

Staining of the skin

The colour from the blue dye might stay in the breast area for several months, but it is not dangerous and will gradually fade.

Radioactivity

The radioactivity from the tracer is safe and there should be no risk of side effects. It contains less radioactivity than you get in everyday life over 3 months.

Not finding the lymph node

Sometimes, the procedure does not find the lymph node containing breast cancer cells. This happens in about 5 out of 100 cases.

In a very small number of cases, the surgeons cannot find the sentinel lymph node because the tracer or dye has not entered the lymph nodes. If this happens, most of the nodes in your armpit will be removed at the time of your original surgery, to make sure that no nodes containing cancer remain.

Other treatment options

An SLN biopsy is not a treatment for breast cancer. It is done to get more information about the stage of your cancer. If you would prefer not to have this done, you do not have to. The alternative would be to remove all the lymph glands from under your arm to get the same information.

After the procedure

We usually do the procedure as a day surgery, so you can usually leave hospital on the same day. The wound will be closed using dissolvable stitches, and be covered by a dressing.

We will tell you how to care for your wound before you leave. The nursing staff will arrange appointments for you to see your breast care nurse and surgeon 7 to 14 days after the procedure. You will be given a letter with this information.

Testing the SLNs

The SLNs are sent to our laboratory to be examined under a microscope. The results take 7 to 14 days, and they will be discussed with you during your next clinic appointment. 

If the SLN contains breast cancer cells

If the SLN contains breast cancer cells, you might need a second surgery to remove all the remaining lymph glands from under your arm. Your doctor will discuss your treatment options with you. This will help you to make an informed decision about what treatment to have.

If the SLN does not contain breast cancer cells

You will not need any more surgery under your arm. 

Support and more information

• Breast cancer support group. This drop-in group for breast cancer patients is held every month at Guy’s Hospital. For more information, contact the breast cancer nurses, phone: 020 7188 0869.
• Breast Cancer Now is a charity with information and support about breast cancer.
• Macmillan Cancer Support is a charity helping everyone with cancer.
• Cancer Research UK is a charity dedicated to researching cancer cures and treatment.
• Department for Work and Pensions have more information about benefits you can get while living with cancer.