Diagnosing melanoma

Removing the spot (excision biopsy)

If the doctor suspects that a spot on your skin may be melanoma, the whole spot is removed (excision biopsy). While this is the preferred type of biopsy to remove the spot, other types of biopsy may be used.

An excision biopsy is usually a simple procedure done in your doctor’s office. Your GP may do this procedure, or you may be referred to a dermatologist or surgeon. For the procedure, you will have an injection of local anaesthetic into the area around the spot to numb the site.

The doctor will use a scalpel to remove the spot and a small amount of healthy tissue (2 mm margin) around it. It is recommended that the entire spot is removed rather than a small sample. This helps ensure an accurate diagnosis of any melanoma found. The wound will usually be closed with stitches and covered with a dressing. You’ll be told how to look after the wound and dressing.

A doctor called a pathologist will examine the tissue under a microscope to work out if it contains melanoma cells. Results are usually ready within a week. Find out more information about what the pathology results mean.

You will have a follow-up appointment to check the wound and remove the stitches. If a diagnosis of melanoma is confirmed, you will probably need a second operation to remove more tissue. This is called a wide local excision. 

Checking lymph nodes

Lymph nodes are part of your body’s lymphatic system. This is a network of vessels, tissues and organs that helps to protect the body against disease and infection. Sometimes melanoma can travel through the lymphatic system to other parts of the body. To work out if the melanoma has spread, your doctor may suggest tests to check the lymph nodes. Not everyone needs these tests.

Ultrasound – a scan used if lymph nodes feel enlarged.

Needle biopsy – if lymph nodes feel enlarged or look abnormal on ultrasound, you will probably have a fine needle biopsy. This uses a thin needle to take a sample of cells from the enlarged lymph node. Sometimes, a thicker sample needs to be removed (core biopsy). The sample is examined under a microscope to see if it contains cancer cells. If cancer is found in the lymph nodes, you may be offered a combination of surgery to remove the lymph nodes and drug therapy. This may be performed at a specialist melanoma unit.

Sentinel lymph node biopsy – when melanoma spreads, often the sentinel nodes are the first place it spreads to. A sentinel lymph node biopsy removes them so they can be checked for melanoma cells.

You may be offered a sentinel lymph node biopsy if you have no lymph nodes that feel enlarged and the melanoma is more than 1 mm Breslow thickness (see below) or is less than 1 mm with high-risk features. A sentinel node biopsy helps find melanoma in the lymph nodes before they become swollen. If your doctor thinks you need a sentinel node biopsy, you will have it at the same time as the wide local excision.

To find the sentinel lymph node, a small amount of radioactive dye is injected into the area where the initial melanoma was found. During the surgery, blue dye is also injected – any lymph nodes that take up both dyes will be removed so a pathologist can check them under the microscope for cancer cells.

If cancer cells are found in a removed lymph node, you may have further tests such as CT or PET–CT scans. The results of this biopsy can help predict the risk of melanoma spreading to other parts of the body. This information helps the multidisciplinary team plan your treatment options and decide whether to recommend drug therapies such as targeted therapy or immunotherapy.

Understanding the pathology report

The report from the pathologist is a summary of information about the melanoma that helps determine the diagnosis, the stage, the recommended treatment and the expected outcome (prognosis). You can ask your doctor for a copy of the pathology report. It may include:

Breslow thickness – This measures the thickness of the tumour in millimetres to its deepest point in the skin. The thicker a melanoma, the higher the risk it could return (recur) or spread to other parts of the body.

Melanomas are classified as:

• in situ – found only in the top layer of the skin (epidermis)
• thin – less than 1 mm
• intermediate – 1–4 mm
• thick – greater than 4 mm.

Ulceration – The breakdown or loss of the outer layer of skin over the tumour is known as ulceration. It is a sign the tumour is growing quickly.

Mitotic rate – Mitosis is the process by which one cell divides into 2. The pathologist counts the number of actively dividing cells within a square millimetre to calculate how quickly the melanoma cells are dividing.

Clark level – This describes how many layers of skin the tumour has grown through. It is rated on a scale of 1–5, with 1 the shallowest and 5 the deepest. The Clark level is less accurate and not used as often now.

Margin – This is the area of normal skin around the melanoma. The report will describe how wide the margin is and whether any melanoma cells were found at the edge of the removed tissue.

Regression – This refers to inflammation or scar tissue in the melanoma, which suggests that some melanoma cells have been destroyed by the immune system. In the report, the presence of lymphocytes (immune cells) in the melanoma indicates inflammation.

Lymphovascular invasion – This means that melanoma cells have entered the lymphatic system or blood vessels.

Satellites – These are small areas of melanoma found separate from, but less than 2 cm away from, the primary melanoma.

Perineural invasion – This is when melanoma cells are found in and around the nerves of the skin.

Further tests

Often, only a biopsy is needed to diagnose melanoma. If pathology results show the melanoma is thicker, you will have scans to find out more about the melanoma. You may also have other tests during treatment or as part of follow-up care after treatment finishes.

Confocal microscopy            

This is a non-invasive type of imaging that allows a dermatologist to see a very detailed and magnified view of your skin cells. The person doing the confocal microscopy uses a handheld device that sends out a low-power laser beam of light, which magnifies cells in the skin by about 1000 times.

Ultrasound            

The person doing the ultrasound will move a handheld device called a transducer across part of your body. The transducer sends out soundwaves that echo when they meet something solid, such as an organ or tumour. A computer turns the echoes into pictures.

CT scan            

A CT (computerised tomography) scan uses x-ray beams to create detailed, cross-sectional pictures. Before the scan, you may have an injection of a liquid dye (called contrast) to make the pictures clearer. The CT scanner is large and round like a doughnut. You will need to lie still on a table while the scanner moves around you.

MRI scan            

An MRI (magnetic resonance imaging) scan uses a powerful magnet and radio waves to create detailed cross-sectional pictures. Before the scan, you may have an injection of a liquid dye (called contrast) to make the pictures clearer. During the scan, you will lie on an examination table that slides into a large metal tube that is open at both ends. The noisy and narrow MRI machine makes some people feel anxious or claustrophobic. Let your medical team know beforehand if you are anxious – you may be offered medicine to help you relax.

PET-CT scan            

A PET (positron emission tomography) scan combined with a CT scan is a specialised imaging test. A glucose solution containing a small amount of radioactive material will be injected into a vein in your arm. Cancer cells can show up brighter on the scan because they take up more of the glucose solution than normal cells do.

Staging melanoma

The pathology report and any other test results will show whether you have melanoma and whether it has spread to other parts of the body. Called staging, it helps your team recommend the most appropriate treatment for you. The melanoma will be given an overall stage of 0–4 (usually written in Roman numerals as 0, I, II, III or IV).

Genomic testing

If the melanoma has spread (stage 3 or 4), you may have genomic tests for a particular gene change (mutation). These gene mutations are due to changes in cancer cells – they occur during a person’s lifetime and are not the same thing as genes passed through families.

About 50% of people with melanoma have a mutation in the BRAF gene, which makes the cancer cells grow and divide faster. About 15% have a mutation in the NRAS gene, which controls how cells divide. C-KIT is a rare mutation affecting less than 4% of people with melanoma.

Genomic tests can be done on the tumour tissue sample removed during surgery. The test results will help doctors work out whether particular drug therapies may be useful.

Prognosis

Prognosis means the expected outcome of a disease. You may wish to discuss your prognosis and treatment options with your doctor, but it is not possible for anyone to predict the exact course of the disease. Instead, your doctor can discuss any concerns you may have.

Melanoma can be treated most effectively in its early stages when it is still confined to the top layer of the skin (epidermis). The deeper a melanoma grows into the lower layer of the skin (dermis), the greater the risk that it could spread to nearby lymph nodes or other organs.

In recent years, newer drug treatments such as immunotherapy and targeted therapy have improved the prognosis for people with melanoma that has spread from the primary site (advanced or metastatic melanoma) or is at very high risk of spreading.