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Skin cancer (melanoma) - Diagnosis

A diagnosis of melanoma will usually begin with an examination of your skin.

As melanoma is a relatively rare condition, many GPs will only see a case every few years. It's important to monitor your moles and return to your GP if you notice any changes.

Seeing a specialist

You'll be referred to a dermatology clinic for further testing if melanoma is suspected.

A dermatologist (skin specialist) or plastic surgeon will examine the mole and the rest of your skin. They may remove the mole and send it for testing (biopsy) to check whether it's cancerous. A biopsy is usually carried out under local anaesthetic. This means the area around the mole will be numbed and you won't feel any pain.

If cancer is confirmed, you'll usually need another operation, to remove a wider area of skin. This is to make sure that no cancerous cells are left behind in the skin.

Further tests

You'll have further tests if there's a concern the cancer has spread into other organs, bones or your bloodstream.

Sentinel lymph node biopsy

If melanoma spreads, it will usually begin spreading through channels in the skin (lymphatics) to the nearest group of glands (lymph nodes). Lymph nodes are part of the body's immune system. They help remove unwanted bacteria and particles from the body. They also play a role in activating the immune system.

Sentinel lymph node biopsy is a test to determine if microscopic amounts of melanoma have spread to the lymph nodes. It's usually carried out by a specialist plastic surgeon. You'll be under general anaesthetic.

A combination of blue dye and a weak radioactive chemical is injected around your scar. This is usually done just before the wider area of skin is removed. The solution follows the same channels in the skin as any melanoma.

The first lymph node the dye and chemical reaches is known as the "sentinel" lymph node. The surgeon can locate and remove the sentinel node, leaving the others intact. The node is then examined for microscopic specks of melanoma. This process can take several weeks.

If the sentinel lymph node is clear of melanoma, it's unlikely that any other lymph nodes are affected. This can be reassuring because if melanoma reaches the lymph nodes, it's more likely to spread elsewhere.

If the sentinel lymph node contains melanoma, there's a risk that other lymph nodes in the same group will also contain melanoma.

Your surgeon should discuss the pros and cons of having a sentinel lymph node biopsy before you agree to having it.

Lymph node dissection or completion lymphadectomy

An operation to remove the remaining lymph nodes in the group is known as a completion lymph node dissection or completion lymphadenectomy.

Other tests

Other tests you may have include:

  • a computerised tomography (CT) scan
  • a magnetic resonance imaging (MRI) scan
  • a positron emission tomography (PET) scan
  • blood tests

Melanoma stages

Healthcare professionals use a staging system called the AJCC system. This describes how far melanoma has grown into the skin (the thickness) and if it has spread. The type of treatment you receive will depend on what stage the melanoma has reached.

The melanoma stages are:

  • Stage 0 – the melanoma is on the surface of the skin
  • Stage 1A – the melanoma is less than 1mm thick
  • Stage 1B – the melanoma is 1-2mm thick, or less than 1mm thick and the surface of the skin is broken (ulcerated) or its cells are dividing faster than usual
  • Stage 2A – the melanoma is 2-4mm thick, or it's 1-2mm thick and ulcerated
  • Stage 2B – the melanoma is thicker than 4mm, or it's 2-4mm thick and ulcerated
  • Stage 2C – the melanoma is thicker than 4mm and ulcerated
  • Stage 3A – the melanoma has spread into 1 to 3 nearby lymph nodes, but they're not enlarged. The melanoma isn't ulcerated and hasn't spread further
  • Stage 3B – the melanoma is ulcerated and has spread into 1 to 3 nearby lymph nodes but they're not enlarged. Or the melanoma isn't ulcerated and has spread into 1 to 3 nearby lymph nodes and they are enlarged. Or the melanoma has spread to small areas of skin or lymphatic channels, but not to nearby lymph nodes
  • Stage 3C – the melanoma is ulcerated and has spread into 1 to 3 nearby lymph nodes and they're enlarged. Or it's spread into 4 or more lymph nodes nearby
  • Stage 4 – the melanoma cells have spread to other parts of the body, such as the lungs, brain or other areas of the skin

Content supplied by the NHS and adapted for Ireland by the HSE.

Page last reviewed: 09/07/2019
Next review due: 09/07/2022