Lymph node biopsy

If there is suspicion that the melanoma might have spread to your lymph nodes, your doctor may recommend that you have:

• a fine needle aspiration biopsy
• a sentinel node biopsy

Fine Needle Biopsy

When there is doubt about the significance of a lump in a group of lymph nodes or an area is identified by some form of radiological imaging, a fine gauge needle can be used to obtain a small amount of tissue for testing (microscopy). It is often the easiest method for obtaining a pathological diagnosis.

Fine needle biopsies are quite common, very simple and usually only take a few minutes. When the area to be investigated is not easy to locate, imaging techniques such as ultrasound and CT scanning are used to guide the biopsy needle.

If palpable, the pathologist identifies the lump and gently stabilises it between his fingers. A fine needle is passed through the skin and into the lump. Cells from the mass are collected in needle. The material (cells) collected in the needle are then spread on a glass microscope slide and examined under a microscope. In addition to standard cytology stains, special examinations with specific antibody based stains can also be used to increase the accuracy of diagnosis.

Sentinel Node biopsy

A sentinel node biopsy provides important information that helps predict the risk of further problems with melanoma spread in the future. This technique is only used for melanomas thicker than 1mm.

In a sentinel node biopsy a substance containing a small amount of radioactivity is injected into the skin around the tumour. The substance passes into the lymph fluid and is trapped by the sentinel node. That lymph node can be removed and examined to see if there are any cancer cells in it.

Examination of the sentinel lymph node or nodes in a patient with a primary melanoma on the skin is an excellent indicator of whether the cancer has spread to the regional lymph nodes (such as the groin, the armpit or the neck). This means that patients who are at the highest risk of later developing melanoma-related problems are identified at an early stage of the disease.

There are three steps to the sentinel node biopsy procedure.

• Lymphoscintigram
• Intraoperative lymphatic mapping with blue dye
• Selective biopsy of lymph nodes identified as ‘sentinel’ nodes

1. Lymphoscintigram

This is a nuclear medicine scan and is also referred to as a ‘lymphatic drainage scan’ or a ‘lymphatic mapping test’. This procedure is often done the day before the operation or on the morning before an afternoon operation. There is no need to fast (no food or drink) specifically for this test but you must be fasted for 6 hours before the due time for the operation.

The first step in performing a lymphoscintigram is a small injection of radioactive tracer around the site of the melanoma. This injection stings for a few seconds. The procedure then involves lying quietly under a scanning machine for several periods of time over 2 – 3 hours.

Scans are done with several different cameras over this period to try to pin-point the exact location of the sentinel node(s). This may include a SPECT/CT camera that shows the tracer in the sentinel node and the CT scan that shows the anatomy of the area. These two technologies can be fused into the one image for more accuracy. Although the tracer is radioactive, there is no significant risk to you from its use. This is because the radiation dose is very small and it loses radioactivity very quickly. In addition, nearly the entire residual radioactivity is removed in the operation.

Side effects

• You will find the isotope injection stings, similar to that of local anaesthetic.
• There may be some residual redness for an hour or two afterwards.
• There may be more than one node identified. Please do not try to wash off the skin markings.
• There is no risk to you from the radioactive marker as the dose is very small and it loses its radioactivity very quickly.

Why is this test necessary?

The lymphatic drainage varies quite markedly from one person to the next. This test is a reliable way of demonstrating where your sentinel nodes are located, often to within a centimetre or so. The SPECT/CT pictures may also help the surgeon to plan the surgical removal of the sentinel node and speed up the procedure.

2. Intraoperative lymphatic mapping with blue dye

The second stage in the sentinel node biopsy is injection with a special blue dye at the time of the surgery. When you are under anaesthetic an injection of Patent Blue V Dye is placed around the melanoma site. This blue dye also migrates in the lymphatic vessels to the sentinel nodes in the same way as the radioactive isotope in the lymphoscintigraphy. The aim is to make it easier to find the lymph nodes identified by the lymphoscintigram by also staining them blue. It provides the surgeon with another guide to locate the correct sentinel nodes.

Side effects

The procedure may be accompanied by discolouration of the injected skin and discolouration of the lymphatic channels leaving the injection site. This discoloured tissue is usually removed as part of the wide local excision procedure but it can mark the skin. Usually any discolouration washes off but it may take a few weeks in some cases. There may be discolouration of the urine lasting no more than 48 hours. There is a possibility of having an allergic reaction, which can be serious, but this is rare.

After the intra-operative lymphatic mapping procedure is performed, the selective surgical removal of the sentinel lymph node(s) will be done. This also happens whilst still under anaesthetic. This procedure is performed at the same time as the wider excision of the original melanoma site. Selective biopsy of sentinel lymph nodes involves an incision over the area(s) of the marked lymph nodes identified by the lymphoscintigraphy. Any lymph nodes with significant radiation from the lymphoscintigraphy or blue dye in them are identified as “sentinel nodes.” They will be surgically removed and sent to the pathologist for very careful examination.

3. Selective Lymph Node Dissection

This procedure is performed in the operating theatre at the same time as the surgical removal of additional skin and tissue around the site of the original melanoma. The sentinel nodes, identified by the blue dye in the lymphatic mapping procedure, are surgically removed and sent to pathology for examination. If melanoma cells are found to be present in a sentinel lymph node, it will be recommended that a complete lymph node dissection, which is the removal of all the lymph nodes in that region, be performed within 4-6 weeks.

Side effects

Side effects which might accompany a selective lymph node dissection may include:

• Pain and/or discomfort at the site of the incision
• Loss of sensation in and around the site of the incision as well as the area immediately adjacent to the site
• Fluid may collect at the incision site and might be accompanied by local infection.
• A small number of patients have temporary swelling of the limb. Occasionally this can persist as a longer term problem.