Sentinel lymph node biopsy is a new surgical procedure in which only the sentinel nodes are removed for evaluation. The advantage of this procedure is that it requires the removal of only one or a limited number of lymph nodes, far fewer than required in an elective lymph node dissection (ELND). Sentinel lymph node biopsy is often conducted in conjunction with lymphatic mapping. In the biopsy procedure, a blue dye is injected into the skin around the tumor, along with the small amount of radioactive substance used for lymphatic mapping. The dye gives the surgeon a visual reference for the process. Once a specific area of lymph drainage has been pinpointed, the sentinel node(s) can be removed and evaluated by a pathologist.

The full results of the sentinel node biopsy may not be known immediately after the procedure. Specialized techniques are often used in the pathologic analysis of sentinel nodes, so unless the node is strongly suspected to be cancerous, the evaluation may take several days to a week.

If the pathologist determines that the sentinel node is negative (no cancer cells are found), no further surgery is performed. Studies show that when the sentinel node is benign, there is a high probability that the rest of the regional lymph nodes are cancer-free as well. The level of probability depends upon the following factors:

• Biopsy site. It is more difficult to get accurate sentinel node biopsies of the head and neck than other sites in the body.
• Experience of the surgeon.
• Technique used to perform the biopsy. The use of radioactive tracer in combination with blue dye offers greater accuracy than either technique used alone.
• Experience and thoroughness of the pathologist.
• Whether a wide local excision has been performed prior to the sentinel node biopsy.

  Important! Wide local excision is a common surgical treatment for early-stage primary melanoma. The procedure changes the lymph drainage patterns of the tumor site and makes it difficult to identify the sentinel lymph nodes accurately. Therefore, lymphatic mapping and sentinel lymph node biopsy should be performed before wide local excision takes place.

If the sentinel node is positive (cancer cells are found in the node), a complete regional lymph node dissection should be performed. In this procedure, all of the lymph nodes in the area of the melanoma are removed for pathologic examination to determine the extent of spread and the number of nodes involved.