Sentinel Lymph Node Biopsy

Why are lymph nodes important in cancer?
Testing the lymph nodes for traces of cancer cells helps the doctor accurately stage the cancer. The stage of a cancer is determined by the size of the original tumor, if the tumor has spread to lymph nodes and if there is spread to other parts of the body. The stage of cancer at diagnosis gives information about prognosis and what treatments may be appropriate.

What is the sentinel lymph node?
A sentinel lymph node is the first lymph node into which a tumor drains, and therefore is the first place to which cancer cells are most likely to spread. In some cases, there can be more than one sentinel node. In breast cancer, for instance, the sentinel node is usually located in the axillary nodes (the lymph nodes under the arm).

What is a sentinel lymph node biopsy?
Previous research has suggested that the sentinel node can be used as a marker to determine if cancer cells have spread to the lymph nodes. In sentinel node biopsy, only one or a few lymph nodes are removed for laboratory analysis when a patient has surgery for certain cancers. It is believed that if the laboratory analysis finds no cancer cells in the sentinel node, the patient is unlikely to have tumor cells in the remaining lymph nodes in that area and thus they would not require removal.

This is advantageous because it reduces the risk of possible complications occasionally seen with traditional lymph node dissection. One of these complications is congestion of lymph fluid in the tissues causing swelling of the arm/leg and is called lymphedema. The other possible complication is decreased sensation in the area. Sentinel lymph node biopsy limits the disruption of the lymphatic structures and nerves.

Who is a candidate for sentinel lymph node biopsy?
Any patient with biopsy proven invasive breast cancer can be considered for sentinel lymph node biopsy. There are several circumstances that make a traditional axillary lymph node dissection a better choice. Patients who have obviously involved lymph nodes should have a complete axillary nodal dissection because it is always best to remove any cancer that is accessible to surgery. Sometimes the location of the primary cancer may interfere with the identification of the sentinel node. Sentinel lymph node biopsy may also be done with other types of cancer, such as melanoma.

How is the sentinel node found?
Patients are taken to the Nuclear Medicine Department. A Nuclear Medicine physician will first use a local anesthetic to numb the area around the tumor site. Next the physician will inject a small amount of a radioactive drug around the tumor site. Pictures (lymphoscintigraphy) are then taken using a gamma camera to identify sentinel node location. The node or nodes are then marked. This procedure usually takes 1 to 2 hours to complete.

How is the sentinel node biopsy performed?
After the lymphoscintigraphy has been completed, the patient will then go to the operating room where, after the patient is asleep, a blue dye is injected around the tumor by the surgeon. The blue dye further assists the identification of the sentinel lymph node. Using a hand held gamma detector, a sort of Geiger counter, the surgeon removes the sentinel node and sends it to the laboratory for careful analysis by a pathologist. The pathologist looks for cancer cells in the tissue of the lymph node.

What happens if there is cancer in the sentinel node?
If even a tiny microscopic deposit of cancer is found during the sentinel node biopsy, then the other lymph nodes could potentially have cancer cells in them. A more extensive lymph node dissection will be performed at that time, or at a later date.

What are the risks associated with sentinel lymph node biopsy?
The biggest risk is that the sentinel node will test negative and not give an accurate picture of the presence of cancer in that area of lymph nodes. The chief safeguard against a false negative result is the experience of the personnel involved, their insistence on a strict criteria for the identification of the sentinel node and their inclination to extend the procedure should the identification techniques not meet strict criteria.

Sentinel lymph node biopsy carries the same risks of any surgery–blood loss and infection, and rarely, reaction to the dye employed.

See related Patient Textbooks about Cancer Center.

See related Patient Topics Blood/Lymphatic System, Cancer Center, Cancer--General, Cancers, Laboratory Tests, Lymphatic Diseases or Procedures and Therapies.

See related Provider Textbooks about Cancer Center.

See related Provider Topics Blood/Lymphatic System, Cancer Center, Cancer--General, Cancers, Laboratory Tests, Lymphatic Diseases or Procedures and Therapies.

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