Sentinel Lymph Node Biopsy

Finding out if cancer has spread

A sentinel lymph node (SLN) biopsy is the best way to find out if the melanoma has spread inside your body, and how far.

The SLN biopsy is an important step in diagnosing melanoma. It is the most accurate way of finding out how far the melanoma may have spread. This helps your doctors select the best treatment for you.

The lymph nodes are glands that are part of the body's immune system, the system that helps protect against disease. Your body has many lymph glands (or nodes), especially in the armpit, neck, and groin.

Why are the lymph nodes important?

A fluid called lymph flows through the lymph glands. Lymph is similar to blood and contains white blood cells, proteins, fats, and other substances. The lymph system helps drain bacteria and other harmful substances from the body. Sometimes, cancer cells can break off from a tumor and enter the lymph. As the fluid flows through the lymph nodes that are near the tumor, the cancer cells can get trapped in the lymph node and begin to grow there.

The first nodes that the lymph fluid from the tumor reaches are called the "sentinel lymph nodes." A sentinel is someone who stands guard. You can think of the sentinel lymph node as the gatekeeper to the rest of the lymph nodes. If the sentinel lymph node has cancer cells in it, there is a chance that the cancer has spread. If the sentinel node does not have cancer cells, the other lymph nodes in that area are probably also cancer-free, and the cancer probably has not spread.

What happens during an SLN biopsy?

SLN biopsy The surgeon will inject a blue dye and a radioactive tracer around the tumor site. The lymph fluid carries the blue dye and tracer away from the tumor to the nearest lymph nodes. The surgeon looks for the lymph node that has blue dye in it (or uses a detector to find the lymph node that has the highest amount of tracer). This is the sentinel lymph node. The surgeon removes this node and a pathologist will test it to see whether it contains cancer cells.

What does the sentinel lymph node tell us?

If the sentinel node is cancer-free, the remaining lymph nodes in that area should also be cancer-free. If the sentinel node has cancer, then other lymph nodes in the area may be removed to stop the disease from spreading further.

An SLN biopsy can also help you avoid unnecessary surgery. For example, if the sentinel node is cancer-free, you will probably not need to have any other lymph nodes removed.

Glossary

Cancer: A general term for more than 100 different diseases that involve the uncontrolled increase of abnormal new cells. These cells form tumors that can destroy surrounding tissue and spread throughout the body.
Cell: The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.
Gland: An organ that makes one or more substances, such as hormones, digestive juices, sweat, tears, saliva, or milk.
Immune system: The complex group of organs and cells that defends the body against infections and other diseases.
Melanoma: A highly malignant type of skin cancer that arises in melanocytes, the cells that produce pigment. Melanoma usually begins in a mole.
Pathologist: A doctor who identifies diseases by studying cells and tissues under a microscope.
Radioactive tracer: A radioactive molecule that can be sent through the body's circulatory or urinary system, with its progress followed by a radiation-sensitive machine.
Tumor: An abnormal mass of tissue that results from excessive cell division. Tumors perform no useful body function. They may either be benign (not cancerous) or malignant (cancerous).