Diagnosing Melanoma: What Is a Sentinel Lymph Node Biopsy?

Sentinel Lymph Node Biopsy or SLN Biopsy is usually done right after melanoma--a type of skin cancer--is diagnosed. An SLN biopsy is the best way to identify the stage of cancer or the extent of the melanoma. In the procedure, a sentinel lymph node is extracted and examined to find out if there is a presence of cancer cells in it.

Lymph Nodes and Sentinel Lymph Node

Lymph nodes or glands are part of the lymphatic system. The lymphatic system consists of lymph vessels that lead to lymph nodes. A clear fluid, referred to as lymph, flows through the vessels similar to the way blood does. The lymphatic system is one of the body's ways to clear the body of bacteria and other harmful substances.

For people with melanoma, there are some occasions when fluids from the tumor contain cancer cells. This happens when cancer cells separate from the tumor and enter the lymph vessels. These cancer cells eventually end up in the nodes where they eventually grow and multiply. The closest lymph node, and the first node where the cancer cells can get trapped into, is called sentinel lymph node. In some occasions, there are more than one sentinel lymph node.

The best way to understand the role of sentinel lymph node, in determining the extent of melanoma and other cancers, is to associate it with the role of a sentinel. By definition, sentinel means "one that keeps guard". A sentinel lymph node is the guard of the entry way to the rest of the lymph nodes. If there are cancer cells in the sentinel lymph node, then, it is likely that there are cancer cells in the surrounding lymph nodes. A Sentinel Lymph Node Biopsy is performed to examine if cancer cells are present.

Sentinel Lymph Node Biopsy Procedure

In an SLN biopsy, the first step is to identify which among the lymph nodes is the sentinel lymph node. This is done by injecting a radioactive substance, a blue dye or both, in the area closest to the tumor. The lymph in the vessel will carry these substances to the nodes. Using a scanner, the sentinel lymph node--the node with the blue dye or the radioactive substance--is identified. An incision will be made to remove the node or nodes. The specimen will be sent to a pathologist for examination.

A positive result in the biopsy of the sentinel lymph node means that cancer cells are present in it. This implies that there is a chance that melanoma has spread to the other nodes or regional lymph nodes. The more extensive the spread is, the higher the level of cancer stage. On the other hand, a negative result in the biopsy means that the cancer cells have not reached the lymph nodes.

Different stages of cancer require different treatment. By identifying the extent of melanoma or the cancer stage, the doctor will be able to recommend an appropriate treatment procedure. Melanoma, at its early stage, can usually be treated with just a surgery.

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