Sentinel Lymph Node Biopsy in Melanoma

A Sentinel Lymph Node Biopsy (SLNB) is a surgical procedure used to help determine if melanoma – or other types other cancers – have spread beyond their site of origin. SLNB is an important tool to help your doctor determine the stage or extent, of your melanoma. This, in turn, will give you additional information to inform future treatment decisions.

What is a Lymph Node?

Lymph nodes are small organs that play an important role in the body’s immune system. Lymph nodes play a crucial role in filtering and monitoring the lymphatic fluid, which carries waste products, pathogens, and immune cells. Lymph nodes are connected to each other throughout the body by lymphatic vessels – or tubes. The lymphatic vessels are a lot like veins that collect and carry blood throughout the body.

Lymph nodes contain white blood cells that help the body fight infection. White blood cells protect against foreign substances such as viruses and bacteria. If detected, these cells will activate an immune response. This is why your lymph nodes may swell when you aren’t feeling well. 

Centralized groups of lymph nodes are found in the neck, underarms, chest, abdomen, and groin.

Lymph nodes are also used to determine if cancer has metastasized, or spread, from its initial site. Many cancers – including melanoma – use the lymphatic system of nodes and vessels to spread. 

Sentinel lymph nodes are the lymph nodes closest to your tumor and first nodes that cancer is likely to have reached.  

What is a SLNB is For?

Sentinel Lymph Node Biopsy (SLNB) is used to determine if melanoma has spread from its initial, or primary site. 

A negative SLNB result suggests that your melanoma has not spread from the skin 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. This information can help a doctor correctly determine the melanoma stage, or the extent of the disease within the body, and develop an appropriate treatment plan.

What Happens During a SLNB?

During a SLNB, doctors first identify the sentinel lymph nodes by injecting a radioactive solution, blue dye, or both near the tumor. You will then be put to sleep using a general anesthesia. In an operating room, your doctor will locate the radioactive or blue lymph nodes, surgically remove them, and then send them to a lab for testing. 

At the lab, the sentinel node is checked for the presence of melanoma by a pathologist. If melanoma is found, the surgeon may remove additional lymph nodes, either during the same procedure or during a follow-up procedure. SLNBs may be performed on an outpatient basis or may require a short stay in the hospital.

A SLNB is usually performed at the same time as the primary tumor is removed. However, the procedure can also be done either before or after removal of the tumor. Talk to your surgeon about any questions or concerns.

What are the benefits of SNLB?

In addition to helping doctors stage melanoma and estimate the risk that tumor cells have developed the ability to spread to other parts of the body, SLNB may help some patients avoid more extensive lymph node surgery. Removing additional nearby lymph nodes to look for cancer cells may not be necessary if the sentinel node is negative for melanoma. All lymph node surgery can have adverse effects, and some of these effects may be reduced or avoided if fewer lymph nodes are removed.

What are the potential harms of SLNB?

SLNB, like other surgical procedures, can cause short-term pain, swelling, and bruising at the surgical site and increase the risk of infection. In addition, some patients may have skin or allergic reactions to the blue dye used in SLNB. In rare instances, swelling – what doctors call edema or more specifically lymphedema – is a result of SLNB. Another potential harm is a false-negative biopsy result—that is, cancer cells are not seen in the sentinel lymph node although they are present and may have already spread to other regional lymph nodes or other parts of the body. A false-negative biopsy result gives the patient and the doctor a false sense of security about the extent of cancer in the patient’s body.  

What Research Says about SLNB in Melanoma:

Researchers have investigated whether patients with melanoma whose sentinel lymph node is negative for cancer and who have no clinical signs of other lymph node involvement can also be spared more extensive lymph node surgery at the time of primary tumor removal. A meta-analysis of 71 clinical studies that involved data from 25,240 patients suggests that the answer to this question is “yes.” This meta-analysis found that the risk of regional lymph node recurrence in patients with a negative SLNB was 5 percent or less.1


This article was adapted from the National Cancer Institute’s factsheet: Sentinel Lymph Node Biopsy.