How is melanoma diagnosed?

Melanoma is diagnosed by physical examination and inspection of the skin, usually followed by biopsy or removal of a suspicious spot or mole. Family history of melanoma will also be considered. Depending on the laboratory results, further tissue samples or other tests, including scans and x-rays, may be needed.

Signs of melanoma

The first sign of a melanoma is usually the appearance of a new spot or a change in an existing freckle or mole. The change may be in size, shape and/or colour. The change is normally noticed over several weeks or months rather than days.

A normal freckle or mole usually has an even colour and a smooth edge. A melanoma often has an irregular edge or surface. It may be spotted with brown, black, blue, red, white and/or light grey.

A freckle or mole that itches or bleeds by itself is sometimes (but not always) a melanoma. A freckle or mole that becomes larger or irregular in shape may be a melanoma. It is normal for new moles to appear and change during childhood and early adulthood.

Having a biopsy

If your doctor suspects you have melanoma, you will probably have a biopsy, where the mole is removed for examination under a microscope.

Biopsy is usually a quick and simple procedure. It may be done by your family doctor or you may be referred to a dermatologist (a skin specialist) or surgeon. The doctor will give you a local anaesthetic and then use a scalpel to remove the mole and some surrounding tissue. You may have stitches to help the wound to heal.

The mole that is cut out is sent to a pathology laboratory for examination. If the tests show you have melanoma, you may have surgery to remove a wider margin of surrounding skin.

Other tests

If you have melanoma, your doctor may recommend other tests. This is, generally, if the original (primary) melanoma was thicker than 1mm and/or may have more chance of spreading to other parts of the body.

The tests may include:

• blood tests: to check your general health
• a chest x-ray: to check for signs of spread to the lungs
• scans: to see if the melanoma has spread to other parts of your body. These may include a liver and abdomen ultrasound scan, a bone scan, a computerised tomography (CT) scan, a positron emission tomography (PET) scan and a magnetic resonance imaging (MRI) scan.
• fine needle aspiration; if you have an enlarged lymph node, your doctor may recommend a fine needle aspiration to see if it is due to the spread of melanoma. In a fine needle aspiration, the doctor (often a pathologist) inserts a needle into the node and draws cells into the syringe. The cells are then examined under a microscope to see if they contain melanoma cells.

Stages of melanoma

The stages of melanoma combine the thickness of the melanoma and the extent of the melanoma (this is determined by the results of the surgery and the tests described above).

The stages are:

• Stage 0: (melanoma in situ) abnormal cells are found in the epidermis
• Stage 1: the melanoma is not more than 2mm thick
• Stage 2: the melanoma is more than 2 to 4mm thick, with no spread to the lymph vessels or nodes
• Stage 3: any melanoma thickness that has spread to lymph vessels or lymph nodes
• Stage 4: the melanoma has spread to other parts of the body.

Knowing the stage of the melanoma helps your doctors plan your treatment. Your doctor will provide more detailed information when discussing treatment.

Measuring the thickness or depth of the melanoma

A pathologist uses two types of measurements to work out the depth of the melanoma - the ‘Breslow thickness’ and ‘Clark level’.

• Breslow thickness measures the thickness or depth of the melanoma microscopically in millimetres from the top layer of skin to the bottom of the melanoma.
• Clark level describes how far melanoma cells have reached through the tissue levels below the skin surface.

Ulceration (breaking the skin’s surface) is also considered when staging a melanoma.

What is the outlook (prognosis) for someone with melanoma?

Melanoma is most likely to be cured when the melanoma is diagnosed and treated in its early stages.

More than 85% of people diagnosed with melanoma 15 years ago are alive and well today with no sign of the disease. This percentage has grown steadily over the years with early detection and treatment; so more people can expect to be cured.

Other factors can influence your prognosis. For example, melanomas on the limbs have a better prognosis than those on the trunk, head or neck. Overall, women seem to fare better than men, although it is unclear why this is the case.

Related topics

Also see Melanoma treatment and Melanoma

Original material provided by the Cancer Society of New Zealand, 2010. Reviewed by everybody, July 2010.