Sentinel node biopsy is a surgical procedure used to determine if cancer has spread outside the main tumor into the lymphatic system. It is most often used to evaluate breast cancer and melanoma. Sentinel nodes are the first lymph nodes that a tumor drains into. Sentinel node biopsy involves the injection of a radioactive tracer that helps the surgeon find the sentinel nodes during surgery. The sentinel nodes are removed and analyzed in a laboratory.

Why is it performed? 

Sentinel node biopsy is recommended for people who have certain types of cancer to determine if cancer cells have spread to the lymph system.

Sentinel node biopsy is used as a routine test for people who have breast cancer or melanoma

A weak radioactive solution is injected near the tumor. This solution is absorbed by the lymphatic system and transported to the sentinel nodes.

This injection is usually performed over several hours or the day before the surgical procedure to remove the sentinel nodes.


Detection is performed with the use of a gamma probe, designed by Intramedical Imaging, which is aimed at the donor site where the radioactive liquid was injected. When the device detects the affected area, it proceeds to the intervention. 

During the procedure:

  • You will probably receive general anesthesia during the procedure.

  • The surgeon begins with a small incision in the area over the lymph nodes.

  • If you have received a radioactive solution prior to the procedure, the surgeon uses a small hand-held instrument called a "gamma detector" to determine if radioactivity has accumulated and to identify the sentinel nodes.

  • If the blue dye is used, the sentinel nodes are stained bright blue, allowing the surgeon to see them.

  • The surgeon then removes the sentinel nodes. In most cases, there are between one and five sentinel nodes, all of which must be removed. These sentinel nodes are then sent to a pathologist to be examined under a microscope for signs of cancer.

In some cases, sentinel node biopsy is performed at the same time as the surgery to remove the tumor. In other cases, sentinel node biopsy may be done before or after surgery to remove the tumor.


After the procedure

You are moved to a recovery room, where the health care team monitors for possible complications from the procedure and anesthesia. If you do not have additional surgery, you will be able to go home the same day.

How quickly you return to your normal activities will depend on your condition. Talk to your doctor.

If you undergo sentinel node biopsy as part of a procedure to remove the tumor, your hospital stay will be determined by the extent of your operation.


If the sentinel nodes are cancer-free, you will not need another lymph node evaluation. If additional treatment is needed, your doctor will use the information from the sentinel node biopsy to develop your treatment plan.

If any of the sentinel nodes contain cancer, your doctor may recommend removing more lymph nodes to determine how many are affected.

In certain cases, a pathologist may examine the sentinel nodes during the procedure. If the sentinel lymph node has cancer, you may need to have more lymph nodes removed right away instead of having another operation.