Sentinel Lymph Node Biopsy (SLNB)

The Importance of The Lymph Nodes

Once the skin biopsy has been done and it has been determined that you have melanoma, the next step is to establish whether or not the melanoma has spread beyond the primary tumor or local tissues.

The presence or absence of melanoma cells in the lymph nodes is one of the most important prognostic factors we have, since it indicates what the melanoma might do in the future as well as the type of treatment you may need.

The Role of The Sentinel Lymph Node Biopsy (SLNB)

SLNB is a specialized procedure done to determine whether any melanoma cells have spread to the sentinel nodes. If the melanoma has spread, it will usually spread to the lymph nodes nearest the area of the primary melanoma. The sentinel lymph nodes are the first of those lymph nodes to receive drainage from the primary tumor, and therefore the ones most likely to have melanoma cells if any of them have spread.

When a SLNB IS Indicated

  • Melanoma is equal to or greater than 1.0mm
  • Ulcerated tumors of any thickness
  • Positive margins
  • Lymphovascular Invasion (seeing cancer cells in the lymphatic channels or blood vessels)
  • Mitotic rate (rate at which cells divide) in young adults

When a SLNB IS NOT Indicated

  • Melanomas less than 0.76mm with no other risk features
  • It is already known that melanoma is in the lymph nodes (Stage III)
  • It has spread to distant organs (Stage IV)

How the SLNB is Done

The SLNB has two parts, a radiology test called lymphatic mapping, and a surgical procedure. A wide local excision should also be performed at the same time.

  • Lymphatic Mapping (Lymphoscintigram) usually involves injecting radioactive dye in the skin around the site of the original melanoma. Then a special camera is used to watch the radioactive material move from where the melanoma was biopsied to the group of lymph nodes the melanoma is most likely to travel to first. These are called the sentinel nodes and in most patients there are between 1 and 5 sentinel nodes.
  • Surgery is performed after the lymphatic mapping has been completed. You will generally receive a second agent (blue dye) that will help visually identify the lymph nodes that have already been detected using the special camera. This two-method approach is more accurate than using either one alone. The surgeon will remove the sentinel nodes and they will be examined by a pathologist under a microscope. It will take several days to get the results.
  • Wide Local Excision is a procedure in which the melanoma, including the biopsy site as well as an area of normal tissue around it (margins), is removed. It is recommended that lymphatic mapping and the sentinel lymph node biopsy be performed before the wide local excision is done.

After The Surgery

The sentinel nodes removed by your surgeon will be examined under a microscope by a dermatapathologist to determine if there is melanoma in the lymph nodes. It has been found that approximately 17% of patients have melanoma in their lymph nodes.

  • If the sentinel lymph nodes do not show cancer, then it is unlikely that the cancer has spread to the other lymph nodes and no further surgery is necessary.
  • If it is shown that there is melanoma in the lymph nodes but no where else in the body, then the remaining lymph nodes in that area may or may not be removed. This is called a complete lymph node dissection. (CLND)

Note: The survival rate of patients is markedly better when the melanoma in the lymph nodes has been found by means of a SLNB, as opposed to being found during a physical exam.

Learn more about CLND

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