Sentinel Node Biopsy

What is a Sentinel Lymph Node Biopsy?

It is often straightforward enough to figure out what lymph node group a melanoma might travel to. Melanomas of the leg colonize the nodes in the crease of the groin (inguinal nodes), and arm melanomas wind up in the arm­pit (axillary nodes). In other areas, the back for example, the melanoma cells’ destination isn’t so obvious. A melanoma of the skin over the right shoulder blade might wind up in the left armpit or the right groin. To find the general destination of such melanomas, physicians have started using a technique called lymphoscintigraphy. This diagnostic technique involves injecting a small amount of radioactive material around the site of a primary melanoma and then scanning different areas–the armpits and groin, for example–to see which one or ones “light up.” The technique is called sentinel lymph node biopsy (or SNLB) and has been designed to determine whether the lymph node that would potentially receive colonies of cells from the primary melanoma has actually done so.

The sentinel node is identified by injecting a radioactive solution and/or a blue-colored dye into the spot where the primary melanoma is (or was). After the injection of dye, waiting half hour or so for the dye to travel through the lymph vessels to the node, the surgeon then reexcises the site of the melanoma. If there is a hot or blue node, it is removed for a pathology examination. If after a few days the node is found not to contain melanoma, then the adjacent nodes are very unlikely to be involved and no further surgery is necessary. If the sentinel node does reveal melanoma, however, the adjacent nodes are usually removed in what is called a complete node dissection, because there are bound to be some other nodes that are involved as well.

What Are the Pros and Cons of Sentinel Node Biopsy?

The SLNB has fulfilled its promise to give both patient and doctor more information more efficiently. Unless the nodes are involved, the patient is spared all but the small incision to check the sentinel node. It is rare that it is complicated by infection, swelling or numbness. In addition, removal of nodes containing melanoma may in itself increase the chance of cure. However, SLNB’s should not be performed for early stage melanomas, those less than .76.

Questions To Ask Your Doctor About Regional Lymph Node Involvement

  1. Can you feel swollen or enlarged regional lymph nodes? If so, do you intend to investigate them further? How?
  2. Do you plan to do lymph node mapping and sentinel lymph node sampling?
  3. Might I need to have surgery to remove a group of lymph nodes (a lymph node dissection)? If so, what are the side effects? Will there be any numbness or swelling associated with the surgery?
  4. Will this be an outpatient or same day hospital procedure or will I need to stay overnight in the hospital?
  5. If I have a node dissection, will it require that a drain be inserted? For about how long?
  6. When will the pathology report be available?
  7. What symptoms should I call you about?
  8. What should I take for pain over the next few days?


Source: Melanoma: Not Just Skin Cancer, by Catherine M. Poole; Contributing editors: Keith Flaherty, MD, DuPont Guerry, MD and Jedd Wolchok, MD, 2015.

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UPDATED: September 1, 2018