Patient education: Sentinel lymph node biopsy for breast cancer (The Basics)

What is a sentinel lymph node biopsy for breast cancer? — This is an operation to check if breast cancer has spread to the lymph nodes.

Lymph nodes are bean-shaped organs found all over the body, including the armpits, neck, and groin. They are part of a network of vessels called the called the "lymphatic system," which carries a clear fluid called "lymph" (figure 1). When breast cancer cells spread, they usually travel first through the lymph to 1 or more lymph nodes in the armpits. These lymph nodes are called "sentinel lymph nodes."

During a sentinel lymph node biopsy ("SLNB"), a surgeon finds, takes out, and checks the sentinel lymph node (or nodes) for cancer cells. Knowing whether cancer is in the sentinel lymph nodes helps the doctor choose the right treatment.

What happens during an SLNB? — The operation is usually done under general anesthesia. This means that you will get medicines to make you unconscious. These might be given through a small tube into a vein (called an "IV") or gases that you breathe through a mask.

Doctors use different techniques to find the sentinel node (figure 2):

●Blue dye – The doctor injects blue dye into your breast near the cancer after you are unconscious in the operating room. The dye travels through the lymph and turns the sentinel node blue.

●A radioactive substance – The doctor injects a radioactive substance into your breast near the cancer and the colored area around your nipple, before you go to the operating room. Then, after you are unconscious, the doctor uses a special device that finds radioactive substances to locate the sentinel lymph node.

●A magnetic substance – The doctor injects a non-radioactive liquid into your breast. The liquid is made of tiny particles that can be identified with a special magnetic probe.

Many surgeons use 2 of these techniques, but some use just 1. After finding the sentinel node, the surgeon makes a small cut to take it out, then sends it to a lab. A different doctor then checks the node for cancer cells. Often, more than 1 sentinel node is found and taken out.

Most people do not have cancer in their sentinel lymph nodes. But if they do, the surgeon might take out other lymph nodes in the armpit to check them as well. If this happens, it is usually during a separate operation.

What happens after an SLNB? — You might have pain, bruising, or bleeding, or get an infection. Your doctor will prescribe pain relievers or other medicines to treat any symptoms.

If your doctor used blue dye, part of your breast will be blue until all of the dye disappears from your body. Your urine will also turn green for 1 day.

In rare cases, people are allergic to the dye used for SLNB. Your doctor will tell you about this risk and answer any questions you have before the operation. The allergic reaction happens in the operating room and is treated right away with medicines given through an IV.

If your doctor used a radioactive substance, the amount of radioactivity is very low and not harmful. It leaves your body quickly through your urine. You are not "radioactive" or dangerous to other people near you.

Your doctor will tell you about the results of the biopsy. They will also tell you if additional lymph nodes need to be removed from your armpit.

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