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How is melanoma diagnosed?

Physical examination

If you notice any changes to your skin, your doctor will examine you, looking carefully at any spots you have identified as changed or suspicious. The doctor will ask if you or your family have a history of melanoma. Using a handheld magnifying instrument called a dermoscope, the doctor will examine the spot more closely and consider the criteria known as “ABCDE”.


AsymmetryAre the halves of each mole different?
BorderAre the edges uneven, scalloped or notched?
ColourAre there differing shades and colour patches?
DiameterIs the spot greater than 6mm across?
EvolvingHas the spot changed over time (size, shape, surface, colour, bleeding, itching)?

Removing the mole (excision biopsy)

If the doctor suspects that a spot on your skin may be melanoma, the whole spot is removed (excision biopsy) for examination by a tissue specialist (pathologist). This is generally a simple procedure done in your doctor’s office. Your GP may do it, or you may be referred to a dermatologist or surgeon.

For this procedure, you will have an injection of local anaesthetic to numb the area. The doctor will use a scalpel to remove the spot and a small amount (2 mm margin) of healthy tissue around it. The wound will usually be closed with stitches. It is recommended that the entire mole is removed rather than a small sample. This helps ensure an accurate diagnosis and accurate staging of any melanoma found.

A pathologist will examine the tissue under a microscope to work out if it contains melanoma cells. Results are usually ready within a week.

You’ll have a follow-up appointment to check the wound and remove the stitches. If a diagnosis of melanoma is confirmed, you will probably need further surgery, such as a wide local excision.

Checking lymph nodes

Lymph nodes are part of your body’s lymphatic system, which removes excess fluid from tissues, absorbs fatty acids, transports fat, and produces immune cells. There are large groups of lymph nodes in the neck, armpits and groin. Sometimes melanoma can travel through the lymph vessels to other parts of the body.

Your doctor may feel the lymph nodes near the melanoma to see if they are enlarged. To test whether the melanoma has spread, your doctor may recommend that you have a fine needle biopsy or a sentinel lymph node biopsy.

Fine needle biopsy – A thin needle is used to take a sample of cells from an enlarged lymph node. Sometimes an ultrasound helps guide the needle into place. The sample is then examined under a microscope to see if it contains cancer cells.

Sentinel lymph node biopsy – If the Breslow thickness (see box below) of the melanoma is over 1 mm or sometimes for people with melanoma between 0.8 mm to 1 mm, you may be offered a sentinel lymph node biopsy. This biopsy finds and removes the first lymph node/s that the melanoma would be likely to spread to (the sentinel node/s). It is usually done at the same time as the wide local excision.

A sentinel lymph node biopsy can provide information that helps predict the risk of melanoma spreading to other parts of the body. This information can help your doctor plan your treatment. It may also allow you to access new clinical trials.

To find the sentinel node/s, a small amount of radioactive dye is injected into the area where the melanoma was found. The surgeon removes the node that absorbs the injected fluid to check for cancer cells. If they are found in the sentinel lymph node, further tests such as ultrasound, CT or PET scans may be done during follow-up and systemic treatment may be offered.