What is a sentinel lymph node biopsy for melanoma?

The short answer: a sentinel lymph node biopsy finds and removes the first lymph node that a melanoma would drain to, so it can be checked under the microscope. It tells us whether the melanoma has started to spread, which helps decide whether you need any further treatment. It is usually done at the same time as the wide local excision, as a day case under general anaesthetic.

Sentinel node biopsy is a big part of my work. I was involved in setting up the service for melanoma at Queen Victoria Hospital in East Grinstead, and I lead the skin cancer multidisciplinary team for Kent and the local Sussex area. These are the questions patients most often ask me about it.

Why is it offered?

When melanoma spreads, the first place it usually goes is the nearest group of lymph nodes. The sentinel node is the first node in that chain. If it is clear, it is unlikely that the melanoma has spread to the lymph nodes. If it contains melanoma cells, finding that early allows us to plan further treatment.

It is not offered to everyone. It depends on the thickness and features of your melanoma. For thin melanomas the chance of spread is very low, so the biopsy is usually not needed. I will explain the benefits and the risks for your situation, and we decide together.

How is the sentinel node found?

Before surgery, a small amount of radioactive tracer is injected into the skin near the melanoma site. It travels through the lymph channels to the sentinel node, and a scan shows where it is. During the operation, a blue dye is also injected. Using a handheld probe and the blue colour, I can find the exact node and remove it through a small incision.

The amount of radioactivity is very small, and it fades quickly.

What happens on the day

The sentinel node biopsy is usually done alongside your wide local excision, which removes a margin of skin around the original melanoma scar to reduce the chance of it coming back. You have a general anaesthetic, and most people go home the same day.

Recovery

• Keep dressings dry for the first few days.
• Stitches are removed or dissolve within about one to two weeks.
• Avoid strenuous activity for the first couple of weeks.
• The blue dye can turn your skin or urine a blue or green colour for a while. This is harmless and temporary.

Risks

The most common problem is a collection of fluid where the node was removed, called a seroma. It sometimes needs draining in clinic. Infection, bleeding and numbness around the scar can happen. Swelling of the limb, called lymphoedema, is uncommon after sentinel node biopsy, but it is something I will discuss with you.

Getting the result

The node is examined in the laboratory, and results usually take two to three weeks. I will go through them with you in person.

If the node is clear, you move on to regular follow-up and skin checks. If it contains melanoma cells, your case is discussed at the specialist skin cancer MDT, and you will be offered further scans and treatment options, which may include drug treatments. Many people in this position do very well.

Can I have it privately?

Yes. Most private insurers cover melanoma treatment, including sentinel node biopsy, and you can also self-fund. Being seen privately can mean faster appointments and seeing the same consultant throughout.

If you have recently been diagnosed with melanoma and want to talk through your options, you are welcome to book a consultation. There is more detail on my melanoma treatment page.