Diagnosing melanoma

A diagnosis of melanoma will usually begin with a visit to your GP who will examine your skin and decide whether you need further assessment by a specialist.

Some GPs take digital photographs of suspected tumours so they can email them to a specialist for assessment.


If your GP decides a suspicious looking mole could be the result of melanoma, you will be referred to a skin specialist (dermatologist) or specialist plastic surgeon for further testing.

The dermatologist or plastic surgeon may do a biopsy. This is a small operation where a suspect mole is removed from your skin to be studied under a microscope. This shows whether the mole is cancerous.

A biopsy is usually carried out under local anaesthetic. The area around the mole will be numbed and you won’t feel any pain. 

If cancer is confirmed, you will usually need a further operation, most often carried out by a plastic surgeon, to remove a wider margin of skin.

Further tests

If there is a concern the cancer could have spread into other organs, bones or your blood stream, further testing will be carried out.

Sentinel lymph node biopsy

If melanoma spreads, it will usually begin spreading in a predictable way through channels in the skin (called lymphatics) to the nearest group of glands (called lymph nodes).

These are the same glands that come up in your neck when you have a cold or sore throat, but they are found everywhere in the body. They are part of the body’s immune system, helping to remove unwanted bacteria and particles from the body.

Microscopic amounts of melanoma can spread through the lymphatics to the lymph nodes. A melanoma on the arm will most often spread to lymph nodes in the armpit, while a melanoma on the leg will most often spread to glands in the groin.

Sentinel lymph node biopsy is a test to determine whether microscopic amounts of melanoma (less than would show up on any X-ray or scan) might already have spread to the lymph nodes. It is usually carried out by a specialist plastic surgeon.

The plastic surgeon injects a combination of blue dye and a weak radioactive chemical around your scar. This will usually be done just before the wider margin of skin is removed. This dye and the radioactivity will follow the same channels in the skin as any melanoma, and the first lymph node that they get to would, logically, be the first lymph node that any cancer would reach – the “sentinel” lymph node.

Using first the radioactivity and then the blue dye, the surgeon can locate and remove the sentinel node (or sometimes nodes), leaving all the others intact. The node is then given to a pathologist who will be asked to examine it to identify or exclude a single microscopic speck of melanoma (this process can take several weeks).

If the sentinel lymph node is clear of melanoma, it is extremely unlikely (although not impossible) that any other lymph nodes are involved. This can be reassuring, since patients whose melanoma has spread to the lymph nodes are much more likely to have their melanoma spread elsewhere.

If the sentinel lymph node contains melanoma, there is around a 20% risk that at least one other lymph node in the same group will contain melanoma. Under these circumstances, you are usually recommended to have a much bigger operation to remove all the remaining lymph nodes in the affected group.

This is recommended because patients whose lymph nodes are affected and left to grow do less well than those whose affected lymph nodes are removed at an early stage. This bigger operation is often called a completion lymph node dissection or completion lymphadenectomy.

Other tests you may have include:

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