Sentinel Node Biopsy

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What is a Lymph Node?

Lymph nodes are small organs in the body that collect harmful substances such as cancer cells, viruses and bacteria. They are part of the lymphatic system, which consists of lymph vessels, ducts and certain white blood cells such as lymphocytes. Together, they carry and distribute a clear substance called lymph, which is found in between cells.

Lymph nodes are shaped like a bean and are normally 1-2 cm in size. They are found in groups in the chest, abdomen, neck, groin and underarms. They become inflamed when an infection is present in the body. The size of the lymph node increases during an infection because production of white blood cells increases. At the lymph node, lymphocytes are initially exposed to foreign substances. An immune response follows.

Using Lymph Nodes to Determine Cancer Progression

The progression of a particular cancer can be determined by examining the lymph nodes closest to the site where the cancer was located. This is done after a cancerous tumor has been identified. If cancer cells are present in the lymph node, it means the cancer has spread and might now be in other parts of the body. To determine the extent, or stage of the cancer, the first lymph node to which the cancer may have spread is examined.

Locating the Sentinel Node

The first lymph node to which a particular cancer is likely to spread is called the sentinel lymph node. In order to locate the sentinel lymph node, the doctor will inject a dye near the primary tumor. As the substance circulates through the body, the doctor will use an imaging device to detect which lymph node collects the substance first. A sentinel node biopsy involves removal of that lymph node, in order to determine if cancer has spread from the primary tumor.

Sentinel Node Biopsy

Once the sentinel node has been located, the doctor will make an incision at the location and remove part of the lymph node. The node is examined by a pathologist to determine if the cells in the tissue are cancerous. If they are, the rest of the sentinel lymph node is removed.

Side Effects and Complications

There are several risks associated with a sentinel node biopsy. Pain and bruising at the biopsy site is common. The dye used to located the sentinel node may produce an allergic reaction. Also, the dye may stain the skin and temporarily change the color of urine.

Removing the lymph nodes hinders the proper functioning of the lymphatic system. Lymphedema may develop, which is a condition characterized by the build up of fluid in a localized area of the body. Numbness, a burning sensation and infection are all possible side effects of sentinel node biopsy.


1. “Sentinel Lymph Node Biopsy: Questions and Answers.” National Cancer Institute. 27 Apr. 2005. Web. 16 Jun. 2010.

2. “Understanding the Lymphatic System.” Lymphomation. Patients Against Lymphoma. 26 Apr. 2010. Web. 16 Jun. 2010.