When Is Sentinel Node Biopsy Indicated in Melanoma?

Medically Reviewed on 1/25/2022
sentinel lymph node biopsy in patients with melanoma
Sentinel node biopsy (SLNB) is done for all patients with melanoma higher than 1 mm in thickness.

To provide optimal staging and prognostic information and maximize management options for node-positive cancer patients, most oncologists believe that sentinel lymph node biopsy (SLNB) should be considered.

SLNB is done for all patients with melanoma higher than 1 mm in thickness and those with melanoma higher than 0.75 mm with other high-risk pathological features.

Other indications include:

  • Patients with the intermediate thickness (1.0 to 4.0 mm) of melanoma lesions
  • Presence of tumor regression factors
  • Presence of ulceration

Some relative indications may include:

  • Younger age
  • Male gender
  • Axial location

Patients with thick melanoma (>4.0 mm) have a high risk of systemic disease (melanoma that has spread) and should have their disease extent assessed after SLNB.

SLNB should still be offered to patients without distant metastases or clinically positive nodes because it provides valuable staging and prognostic information. The goal of SLNB is to see if early detection and management of regional nodes can help patients live longer.

Why should I undergo sentinel lymph node biopsy if I have melanoma?

The lymphatic system (that consists of vessels and nodes) is a collection of channels in our bodies that drains fluid from our tissues. Melanoma cells can travel through these channels. Within the lymphatic system, lymph nodes act as a filter that checks what passes through.

  • The sentinel node is the first lymph node to drain lymph from the melanoma site.
  • The presence of cancer cells in the sentinel lymph node is important for melanoma staging and prognosis.
  • If melanoma cells are found in the sentinel node, the surgeon can discuss several treatment options with the patient.

A sentinel lymph node biopsy is a diagnostic tool and not a treatment. Information from the sentinel node is used to create a personalized treatment plan for melanoma.

What happens during sentinel lymph node biopsy?

As an outpatient procedure, sentinel lymph node biopsy (SLNB) is performed under general anesthesia. It's usually done at the same time as the primary tumor is removed.

The surgeon may inject a blue dye into an area near the tumor or where the tumor was removed just before SLNB. The surgeon looks for lymph nodes stained blue by the dye or uses a special probe to locate radioactive lymph nodes.

They remove the sentinel lymph node through a small cut (incision) in the skin above the group of lymph nodes closest to the primary tumor. They send the sentinel lymph node to a lab for microscopic examination.

  • Negative result:
    • The absence of cancer cells in the sentinel lymph node is indicated by a negative SLNB result. This is a typical outcome.
    • The rest of the lymph nodes in the area are not removed because they are unlikely to contain cancer.
    • However, when the result is negative, there is still a chance that cancer has spread to other lymph nodes (called a false-negative result).
  • Positive result:
    • A positive SLNB result indicates the presence of cancer cells in the sentinel lymph node. This is an unusual outcome.
    • A lymph node dissection may be performed after an abnormal result to remove more lymph nodes from the area.

Depending on the result, the doctor will decide if the patient needs more tests, any treatment, or follow-up care.

Before SLNB, the sentinel node is identified and removed using one of the two methods that differ in the way the sentinel node is located. A blue dye is injected in one method, whereas a radioactive material and gamma counter is used in the other. Techniques are frequently used in tandem.

Benefits of SLNB include

  • It has the potential to reduce the amount of surgery required.
  • It lowers the risk of long-term complications from more extensive surgery.
  • It provides more accurate staging and prognostic data to aid in treatment decisions.
  • It's even been shown to help patients live longer.

Side effects of SLNB include

  • Pain
  • Bruising or swelling at the site of surgery
  • Infection
  • Numbness or tingling
  • Lymphedema (swelling around the procedural area)
  • Problems moving a part of the body close to the site of surgery such as an arm or a shoulder
  • An allergic reaction to the dye and or anesthesia

The sentinel lymph node is the one closest to the site of cancer's onset. Primary cancer or tumor is the site where cancer first appears. There may be more than one sentinel lymph node in some cases.

Before spreading to other parts of the body, cancer cells may appear in the sentinel lymph node.


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Should I be worried if I am diagnosed with melanoma?

Melanoma is known for its ability to spread. This cancer is sometimes associated with black and irregular edges, but this isn't always the case. People expect it to bleed and become sore. However, these symptoms may only appear in the later stages of the disease.

The early stages of melanoma may appear quite different.

  • The appearance of the skin can vary greatly. It frequently resembles early aging spots where one part has become irregular. The appearance of a darker section on one edge, or a mole that appears to be changing, is a useful clue.
  • If a patient notices a brown blemish on their skin that has changed or darkened in one area, they must consult with an experienced dermatologist.
  • Although the majority of melanomas on the skin are dark in color, some rarer forms can present as a firm pinkish red lump.
  • Melanoma accounts for more than 75 percent of all skin cancer deaths.
  • Surgery may be an option for treatment. To prevent cancer from spreading, every cancerous cell must be removed, which may necessitate the removal of a significant amount of skin.
  • When melanoma spreads, conventional cancer treatments (such as chemotherapy) are used, but they may not be effective.
  • If detected at an early stage, it is curable.

Because of the invasive nature of melanoma, sentinel lymph node biopsy (SLNB) is frequently recommended in the early stages.

SLNB is a surgical staging procedure used to determine whether there is low volume nodal metastasis in the draining lymph node field in patients with primary cutaneous melanoma who are clinically lymph node-negative.

What are the treatment options for melanoma?

Melanoma, the deadliest type of skin cancer, accounts for only about 4 percent of all skin cancer cases but accounts for 79 percent of skin cancer deaths.

Melanoma treatment is primarily determined by the stage of cancer at the time it is discovered. The stage provides a common language for doctors and patients to understand how advanced the cancer is, where it is located and what treatment options are available.


  • The primary treatment of all stages of melanoma is surgery to remove the tumor.
  • To remove the melanoma and some of the normal tissue surrounding it, wide local excision is used.
  • To cover the wound caused by surgery, skin grafting (taking skin from another part of the body to replace the skin that is removed) may be performed.
  • It is critical to determine whether cancer has spread to the lymph nodes. To check for cancer in the sentinel lymph node, lymph node mapping and sentinel lymph node biopsy are performed.

After the doctor removes all visible melanoma at the time of surgery, some patients may be given chemotherapy to kill any remaining cancer cells. Adjuvant therapy refers to chemotherapy administered after surgery to reduce the likelihood of cancer recurrence.

To improve the patient's quality of life by controlling symptoms, surgery to remove cancer that has spread to the lymph nodes, lung, gastrointestinal tract, bone, or brain may be performed.


  • Chemotherapy is a cancer treatment that uses drugs to halt the growth of cancer cells, either by killing them or preventing them from dividing.
  • Chemotherapy drugs enter the bloodstream and can reach cancer cells throughout the body when taken orally or injected into a vein or muscle (systemic chemotherapy).
  • Chemotherapy drugs primarily affect cancer cells in the cerebrospinal fluid, an organ, or a body cavity such as the abdomen when administered directly into those areas (regional chemotherapy).

The way the chemotherapy is given depends on the type and stage of the cancer being treated.

Radiation therapy

  • Radiation therapy is a type of cancer treatment that uses high-energy X-rays or other types of radiation to either kill or prevent cancer cells from growing. 
  • External radiation therapy uses a machine located outside the body to direct radiation toward the cancerous area.
  • External radiation therapy is used to treat melanoma and can be used as palliative care to alleviate symptoms and improve quality of life.

Immunotherapy or biological therapy

  • Immunotherapy is a cancer treatment that uses the patient's immune system to combat the disease.
  • Substances produced by the body or created in a laboratory are used to augment, direct, or restore the body's natural anti-cancer defenses.

Targeted therapy

  • Targeted therapy is a type of cancer treatment in which drugs or other substances are used to identify and attack specific cancer cells.
  • Targeted therapies are less likely to harm normal cells than chemotherapy or radiation therapy.

Vaccine therapy (still under research)

  • Vaccine therapy uses a substance or group of substances to stimulate the immune system into locating and killing the tumor.
  • Vaccine therapy is being researched for the treatment of stage III melanoma that can be surgically removed.

Participating in a clinical trial may be the best treatment option for some patients. Clinical trials, which are a component of cancer research, are conducted to determine whether new cancer treatments are safe and effective, or if they are better than the standard treatment. 

Many of today's standard cancer treatments are based on earlier clinical trials. Patients who participate in a clinical trial may receive standard care or be among the first to receive a novel treatment.

Patients who participate in clinical trials help improve the way cancer is treated in the future. Even when clinical trials do not result in effective new treatments, they frequently answer important questions and help move research forward.

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Medically Reviewed on 1/25/2022
Image Source: iStock Images

Sentinel lymph node biopsy is indicated for patients with thick clinically lymph node-negative melanoma: https://pubmed.ncbi.nlm.nih.gov/25677366/

Sentinel Lymph Node Biopsy and Management of Regional Lymph Nodes in Melanoma: American Society of Clinical Oncology and Society of Surgical Oncology Clinical Practice Guideline Update: https://ascopubs.org/doi/10.1200/jco.2017.75.7724

The Role and Necessity of Sentinel Lymph Node Biopsy for Invasive Melanoma: https://www.frontiersin.org/articles/10.3389/fmed.2019.00231/full

Melanoma Treatment (PDQ®)–Patient Version: https://www.cancer.gov/types/skin/patient/melanoma-treatment-pdq

Melanoma: https://www.cancer.org.au/cancer-information/types-of-cancer/melanoma