Sentinel Lymph Node Biopsy

What is a sentinel lymph node biopsy?


Our bodies have a network of lymphatic channels and nodes that carry a watery clear fluid called lymph. This fluid flows throughout our bodies, similar to the way blood vessels carry blood to all parts of the body. The lymph fluid contains white blood cells, which help us fight infections. Cancer cells can travel in the lymph system as well. Because the lymph system runs throughout the body, these cancer cells may spread to other areas of the body.


A sentinel lymph node biopsy – also known as a sentinel lymph node mapping and excision – helps trace the path where a breast cancer may drain and what lymph nodes it may drain to first. These first lymph nodes are called the sentinel lymph nodes.


This surgery helps determine if cancer cells have spread to any lymph nodes and may be used to determine the stage of some breast cancer. It may be done on the same day as another cancer surgery or it may be scheduled separately.


After the sentinel lymph nodes are identified during surgery, they are removed and sent to a pathologist, who will determine if cancer is present. The nodes often do not contain cancer cells. However, the entire node must be removed to determine this.


How is the test done?


Before surgery, patients receive an injection of a radioactive tracer (dye) near their breast. The injection may cause some pain. This injection and related X-rays done in the Nuclear Medicine Department are referred to as lymphoscintigraphy. The radiologists will take images to follow the radioactive tracer as it travels through the lymphatics and will show which lymph node(s) have taken up the radioactive dye.


Your sentinel node surgery may take place the same day as the radioactive tracer injection or the following day. In the operating room, the surgeon will inject a blue dye near the area of the cancer about 15 minutes before the surgery. During the surgery, your doctor looks at the lymph nodes to identify which ones have the blue dye in them and also uses a probe to detect the presence of the radioactive tracer in your lymph nodes. Some lymph nodes "pick" up both or only one of the dyes. Two dyes are used to make sure the sentinel node(s) can be identified.


Almost everyone has some lymph nodes (an average of two) that take up the dye(s). Those that take up the dye are the lymph nodes where a cancer would most likely spread first; they are called the sentinel lymph nodes. Your surgeon removes these lymph nodes and sends them to a pathologist.


The presence of dye in the sentinel lymph nodes does not mean there are cancer cells in the lymph node. It only means that if your cancer was going to spread, these are the lymph nodes it would go to first. Whether cancer is present in the sentinel lymph nodes can be determined only by the pathologist after the lymph nodes are removed and examined under a microscope.


What can I expect after the test?


If you are having additional surgery, such as breast cancer removal, your surgeon will complete the surgery at the sentinel node location and the primary cancer location. The sentinel node surgery takes only 30 to 40 minutes.


After your surgery, you may notice that your urine is blue or green from the dye. This will go away within 24 hours. Some people get a very faint blue coloring to their skin after surgery as well. This also will go away within 24 hours. You may notice some temporary numbness in the surgical area.