How is melanoma diagnosed?
The first step in diagnosing a melanoma is a close examination of the spot. If the spot looks suspicious, the doctor will remove it so it can be checked in a laboratory. In some cases, further tests will be arranged.
If you notice any changed or suspicious spots, your doctor will look carefully at your skin. 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 spots more closely and consider the signs known as the ABCDE guidelines.
ABCDE signs of melanoma
Asymmetry – Are the halves of each spot different?
Border – Are the edges uneven, scalloped or notched?
Colour – Are there differing shades and colour patches?
Diameter – Is the spot greater than 6 mm across, or is it smaller than 6 mm but growing larger?
Evolving – Has the spot changed over time (size, shape, surface, colour, bleeding, itching)?
Some types of melanoma, such as nodular and desmoplastic melanomas, don’t fit the ABCDE guidelines, so your doctor may also assess whether the
spot is raised, firm or growing.
If the doctor suspects that a spot on your skin may be melanoma, the whole spot is removed (excision biopsy) so it can be examined by a specialist doctor called a pathologist.
An excision biopsy 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 the 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 of healthy tissue (2 mm margin) 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 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.
Lymph nodes are part of your body’s lymphatic system, which helps to protect the body against disease and infection. The lymphatic system is a network of vessels, tissues and organs. There are large groups of lymph nodes in the neck, armpits and groin. Sometimes melanoma can travel through the lymphatic system to other parts of the body.
To work out if the melanoma has spread, your doctor will feel the lymph nodes closest to the melanoma and may recommend an ultrasound and a fine needle biopsy or a sentinel lymph node biopsy.
Fine needle biopsy – If any lymph nodes feel enlarged or lumpy, you will probably have a fine needle biopsy. This uses a thin needle to take a sample of cells from the enlarged lymph node. The sample is then examined under a microscope to see if it contains cancer cells. If cancer is found in the lymph nodes, you may need to have surgery to remove them.
Sentinel lymph node biopsy – You may be offered a sentinel lymph node biopsy if the lymph nodes do not seem enlarged but the melanoma is considered high risk. This biopsy finds and removes the first lymph node that the melanoma would be likely to spread to (the sentinel node). Sometimes more than one sentinel node is found and removed. The removed lymph nodes are then checked for melanoma cells under a microscope. A sentinel lymph node biopsy is usually done 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. The surgeon removes any lymph nodes that take up the dye so they can be checked 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 and further treatment may be offered. The results of a sentinel lymph node biopsy can help predict the risk of melanoma spreading to other parts of the body. This information helps your doctor plan your treatment. It may also allow you to take part in a new clinical trial.
If you have a melanoma removed, the report from the pathologist will provide your treatment team with information to help work out how far the melanoma has spread (the stage), the recommended treatment plan and the expected outcome (prognosis).
You can ask your doctor for a copy of the pathology report and discuss the results with them. The following factors may be included:
Breslow thickness – This is a measure of the thickness of the tumour in millimetres to its deepest point in the skin. The thicker a melanoma, the more likely it could return (recur) or spread to other parts of the body.
Melanomas are classified as:
- in situ – found only in the outer layer of the skin
- 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 of rapid tumour growth.
Mitotic rate – Mitosis is the process by which one cell divides into two. The pathologist counts the number of actively dividing cells to calculate how quickly the melanoma cells are dividing.
Clark level – This describes how many layers of skin the tumour has gone through. It is rated on a scale of 1–5, with 1 the shallowest and 5 the deepest. (On the report, the Clark level will be written in Roman numerals as I, II, III, IV or V.) Breslow thickness is much more important than Clark level in working out the stage of a melanoma.
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.
Many people will need only a biopsy. Some people will have further tests such as blood tests or imaging scans to get more information about the melanoma. You may also have these tests during treatment or as part of follow-up care after treatment finishes. Imaging scans use different methods to create images of the inside of the body:
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 the 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 the 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 scan can be noisy, but you will usually be offered headphones or earplugs.
PET–CT scan – A PET (positron emission tomography) scan combined with a CT scan is a specialised imaging test. You will be injected in the arm with a glucose solution containing a small amount of radioactive material. Cancer cells show up brighter on the scan because they take up more of the glucose solution than normal cells do.
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This information is reviewed by
This information was last reviewed January 2021 by the following expert content reviewers: A/Prof Robyn Saw, Surgical Oncologist, Melanoma Institute Australia, The University of Sydney and Royal Prince Alfred Hospital, NSW; Craig Brewer, Consumer; Prof Bryan Burmeister, Radiation Oncologist, GenesisCare Fraser Coast and Hervey Bay Hospital, QLD; Tamara Dawson, Consumer, Melanoma & Skin Cancer Advocacy Network; Prof Georgina Long, Co-Medical Director, Melanoma Institute Australia, and Chair, Melanoma Medical Oncology and Translational Research, Melanoma Institute Australia, The University of Sydney and Royal North Shore Hospital, NSW; A/Prof Alexander Menzies, Medical Oncologist, Melanoma Institute Australia, The University of Sydney, Royal North Shore and Mater Hospitals, NSW; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Paige Preston, Chair, Cancer Council’s National Skin Cancer Committee, Cancer Council Australia; Prof H Peter Soyer, Chair in Dermatology and Director, Dermatology Research Centre, The University of Queensland Diamantina Institute, and Director, Dermatology Department, Princess Alexandra Hospital, QLD; Julie Teraci, Clinical Nurse Consultant and Coordinator, WA Kirkbride Melanoma Advisory Service, WA.