Melanoma has the ability to travel to distant sites of the body through the lymphatic system. One of the most important prognostic indicators in a melanoma is an accurate staging of the lymph nodes. Lymph nodes are small round organs that are part of the body's lymphatic system. They are found widely throughout the body and are connected to one another by lymph vessels. A sentinel lymph node is the term given to the first lymph node to which melanoma cells are most likely to spread from a primary tumor. Sometimes, there can be more than one sentinel lymph node.
A sentinel lymph node biopsy (SLNB) is a procedure that is performed in the operating room in which the sentinel lymph node is identified, removed, and examined to determine whether melanoma cells are present.
• A negative SLNB result suggests that cancer has not developed the ability to spread to nearby lymph nodes or other organs.
• A positive SLNB result indicates that cancer is present in the sentinel lymph node and may be present in other nearby lymph nodes and, possibly, other organs.
Given that melanoma can travel to multiple lymphatic basins depending on the location of the primary lesion, a nuclear medicine procedure called lymphoscintigraphy is performed the evening prior or the morning of the sentinel lymph node. During the lymphoscintigraphy, a radiotracer is injected around the melanoma just beneath the skin using a very small needle. Immediately after the injection, a special camera called a gamma camera will take a series of images of the area of the body being studied. When it is time for the imaging to begin, the camera or scanner will take a series of images. The camera may rotate around you or it may stay in one position and you will be asked to change positions in between images. While the camera is taking pictures, you will need to remain still for brief periods of time. In some cases, the camera may move very close to your body. This is necessary to obtain the best quality images. Information from the pictures obtained will identify the location of the sentinel lymph nodes.
The actual sentinel lymph node biopsy is performed in the operating room. Blue dye is injected into the skin around the melanoma which travels through the lymphatic system and stains the sentinel lymph nodes blue. The surgeon then finds the sentinel node that is stained with the blue dye and contains the radiotracer from the lymphoscintigraphy and removes the node. The sentinel node is then checked for the presence of melanoma by a specialized pathologist.
The sentinel lymph node is performed at the same time the primary melanoma is with a wide local resection.