Sentinel lymph node biopsy

Lymph nodes are bean shaped structures. Some normal nodes are as small as the head of a pin; others can be as large as a lima bean. The lymph glands and vessels serve as channels through which liquid around the cells (extra cellular fluid) is returned into the blood stream. Lymph nodes act to filter these liquids of bacteria, fungi, and viruses. White blood cells and antibodies in the lymph nodes can kill these invaders, which can cause disease.

Why are lymph nodes important in cancer?

Testing the lymph nodes for traces of cancer cells helps the doctor 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 directs what treatments should or could be used.

What is the sentinel lymph node?

A sentinel lymph node is the first lymph node into which a tumor drains, and is the first place 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 no cancer cells are found in the sentinel node, the patient is unlikely to have tumor cells in the other lymph nodes in that area and they would not need to be removed.

This is good because it lowers the risk of possible complications seen with the removal of a large number of lymph nodes. One of these complications is build-up 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 damage to the lymphatic system and nerves.

Who is a candidate for sentinel lymph node biopsy?

Any patient with invasive breast cancer or melanoma can be considered for sentinel lymph node biopsy. People who have known involved lymph nodes should have axillary nodes removed because it is always best to remove all cancer possible at the time of surgery. Sometimes the location of the cancer makes it hard to identify the sentinel node. Researchers are looking at the use of sentinel lymph node biopsy in patients with Gynecologic, prostate, bladder, thyroid, head and neck, colon, rectum, stomach, non-small cell lung, and Merkel cell cancers.

How is the sentinel node found?

People are taken to the Nuclear Medicine Department. A Nuclear Medicine doctor will number the area around the tumor site. Next the doctor will inject a small amount of radioactive drug around the tumor site. Pictures (lymphoscintigraphy) are then taken using a special camera to locate the sentinel node. The node or nodes are then marked. This procedure takes about 1 to 2 hours.

How is the sentinel node biopsy performed?

After the lymphoscintigraphy is done, the patient will go to the operating room. After the patient is asleep, a blue dye is injected around the tumor by the surgeon. The blue dye further helps show 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 deposit of cancer is found during the sentinel node biopsy, then the other lymph nodes could have cancer cells in them. Breast cancer doctors used to remove those nodes, but studies have shown that further node removal does not change prognosis so now they are not removed. The lymph nodes are still removed in melanoma patients.

What are the risks associated with lymph node biopsy?

The biggest risk is that the sentinel node will test negative but there may be cancer cells in other lymph nodes. To protect against this, all involved need to follow strict guidelines and procedures to find the sentinel node. If there is any doubt or concern, more lymph nodes will be removed and tested.

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

Source: UI Cancer Information Services

Last reviewed: 
January 2018

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