Melanoma Diagnostic Overview

Sentinel Lymph Node Biopsy

Since melanoma often quickly spreads to nearby lymph nodes, the nodes are examined once a diagnosis is confirmed. If the physician sees or feels that nodes are enlarged, or if imaging strongly suggests enlargement, the cancer may have spread to local lymph nodes. If nodes do not appear enlarged, a sentinel lymph node biopsy (SLNB) is a common way to determine whether the disease has reached the lymph nodes.

What is a lymph node?

Lymph nodes are glands that are part of your lymphatic system where your white blood cells form, and where lymph, a clear fluid containing your white blood cells, is filtered.

What is a sentinel lymph node?

Sentinel nodes are the first lymph nodes that drain lymph fluid from the primary tumor, and it is believed when the cancer spreads, it will show up first in these lymph nodes. In most areas of the body, there are only one or two sentinel lymph nodes. In the head and neck, there are typically two to five sentinel lymph nodes.

What happens during an SLNB?

A sentinel lymph node biopsy is a minimally invasive procedure with a low risk of side effects. It provides important information to guide doctors in staging and treating the disease.

Here’s what to expect

  1. The medical team begins by injecting a tracer material into the tumor site to help the surgeon locate the sentinel nodes during the procedure. Sometimes the medical team will also inject a blue dye into the tumor so that the nodes appear blue during the procedure.
  2. Using an instrument that detects the tracer, the path from tumor to nearby sentinel nodes is mapped. Cancer cells from the tumor would likely follow this path.
  3. The sentinel nodes are removed and analyzed in a lab.
  4. If cancer cells are discovered in the lymph nodes, the surgeon removes all local lymph nodes or destroys them with radiation therapy. Often, both procedures are performed: the lymph nodes are completely removed followed by radiation to help prevent recurrence.

Benefits of SLNB

Once melanoma travels to the lymph nodes it becomes harder to treat. SLNB helps patients by:

  • Identifying where cancer cells may have spread.
  • Revealing cancer cells that are not visible and cannot be detected through physical examination or imaging.
  • Helping the doctor predict the patient’s chance or recovery, also known as prognosis.
  • Guiding the doctor to determine the best treatment options.
  • Preventing a local recurrence by removing or destroying cancerous nodes.

Reviewed by:  Brittany Barber, MD

Last reviewed: June 2019