A melanoma is a serious form of skin cancer, the first symptom of which is a change in an existing mole or freckle, or the appearance of a new mole or freckle. Melanoma can be successfully treated if detected early. New Zealand has one of the highest incidences of melanoma in the world.
What is melanoma?
Melanoma is the most aggressive form of skin cancer and the fourth most common cancer in New Zealand. Each year approximately 2500 people are diagnosed with the condition and over 300 die from it. In New Zealand melanoma accounts for 80% of all skin cancer deaths. Melanomas can occur at any stage in life, though it is rare for melanomas to occur in children and teenagers. The chances of developing a melanoma increase with age. Melanoma is the most commonly registered cancer in men aged 25-44 and the second most commonly registered cancer in women of the same age group.
Melanomas develop from specialised skin cells called melanocytes. These cells produce melanin, which is the pigment that causes the skin to darken when exposed to the sun. Melanocytes are found in the outer layer of the skin (the epidermis). Non-cancerous growth of melanocytes produces moles and freckles.
Melanomas occur when melanocytes divide uncontrollably and form a mass of cancerous cells. While the reason this occurs is not fully understood, excessive exposure to the ultraviolet (UV) radiation in sunlight, and from other sources, is thought to be a contributing factor.
Melanomas can occur in areas of the body not necessarily exposed to UV radiation including the eye; palms of hands or soles of feet; the mouth, vulva or vagina; under fingernails and toenails.
Most melanomas can be cured if detected and treated early. It is therefore important to seek medical advice if any change in a mole or freckle is noticed. If left untreated melanomas can spread to deeper layers of skin and to other areas of the body via the lymphatic system or blood. If another tumour develops as a result of the melanoma it is known as a secondary or metastatic tumour.
As melanomas can occur in places that receive little or no exposure to sunlight, UV radiation is not the only contributing factor. Other factors that can increase the risk of developing a melanoma include:
- Having fair skin
- Being exposed to large amounts of UV radiation eg: sunlight, tanning machines
- Having had one or more severe sunburns – particularly in childhood
- Having a large numbers of moles or freckles
- Having a family history of melanoma
- Having had a previous melanoma
Melanomas are uncommon in Maori, Pacific Island and Asian New Zealanders.
Signs, symptoms, diagnosis
The first sign of a melanoma is a change in an existing mole or freckle, or the appearance of a new mole or freckle. The most common site for melanomas to occur in men is the back (approximately 40%) and the most common site for melanomas to occur in women is the leg (approximately 40%).
If any changes or new moles or freckles are noticed, consult a doctor promptly. The doctor will examine the suspicious mole or freckle and look for any of the characteristic signs that may indicate that it is a melanoma. They will also examine the rest of the body for any other suspicious moles or freckles. When assessing a suspicious freckle or mole, doctors may use one or both of the following assessment criteria.
ABCDE of melanoma:
A for Asymmetry - the mole is not symmetrical
B for Border - the border of the mole or freckle is irregular
C for Colour - variation in colour
D for Diameter - the mole is greater than 6mm in diameter
E for Elevation or Evolving - there is a change in the height of the mole or it is enlarging or changing.
Glasgow 7-point checklist:
Change in size
Diameter greater than 7mm
Change in sensation.
If a mole or freckle has any of the characteristics described in either of the above assessment tools, the lesion should be surgically removed and sent to a laboratory for examination under a microscope. This will enable an accurate diagnosis to be made.
If it is confirmed that the lesion is a melanoma, the examining pathologist will report on the height and depth of the melanoma. This is part of the classification or “staging” of the melanoma.
Staging of melanomas
The "stage" of a melanoma will indicate if it has spread from its original site in the skin. Information required to assess the stage of a melanoma includes the depth of penetration of the tumour through the skin. This may be described in two ways. Clark's Level is an assessment of how many skin layers the tumour has invaded, while Breslow Thickness is a microscopic measurement of the thickness of the tumour.
Other information required to accurately stage a melanoma is derived from additional examinations and tests such as:
- Physical examination
- Blood tests
- Scans eg: ultrasound, CT, MRI or PET scans.
These tests can assess whether the melanoma has spread to surrounding lymph nodes or to other parts of the body.
In New Zealand most melanoma specialists refer to the American Joint Committee of Cancer (AJCC) cutaneous melanoma staging guidelines when staging a melanoma. The stages are:
- Stage 0 - in situ melanoma (only occurring in the top layer of the skin)
- Stage 1 - thin melanoma: less than or equal to 2mm in thickness (or less than or equal to 1mm in thickness if ulceration is present)
- Stage 2 - thick melanoma: greater than 2mm in thickness (or greater than 1mm in thickness if ulceration is present)
- Stage 3 - melanoma spread to involve local lymph nodes
- Stage 4 - distant metastases have been detected
The stage of a melanoma will influence what treatment is undertaken.
Melanomas are surgically removed. The extent of the surgery required will depend on the size, thickness and site of the melanoma. An early melanoma may not require extensive surgery and can usually be removed under a local anaesthetic. An area of healthy skin surrounding the melanoma will also be removed to ensure that all cancerous cells are removed. Most people who develop a melanoma can be successfully treated with surgery alone.
If the melanoma has penetrated deeper layers of the skin, a greater area of surrounding tissue will need to be removed. It may also be necessary to biopsy or remove lymph nodes in the area. If the surgery is extensive, skin grafts to cover the removed area of skin may be required.
If the melanoma has spread to other parts of the body, other forms of treatment, or a combination of treatments, may be necessary. Treatment may include:
- Chemotherapy - the use of drugs to destroy cancer cells
- Radiotherapy (also called radiation therapy) - the use of high powered energy beams, such as x-rays, to destroy cancer cells
- Immunotherapy - the use of drugs that stimulate the body's immune system to fight the cancer cells, eg: nivolumab (Opdivo) and pembrolizumab (Keytruda)
- Targeted therapy - the use of drugs that exploit specific vulnerabilities in how cancer cells divide and grow, eg: dabrafenib (Tafinlar) and vemurafenib (Zelboraf).
In cases where the melanoma has spread, a number of health professionals may be involved in treatment. This can include:
- Family doctor
- Dermatologists (skin specialists)
- Oncologists (cancer specialists)
- Plastic surgeons (specialist surgeons who reconstruct damaged areas of the body)
- Specialist cancer nurses
- Radiation therapists
Following diagnosis and treatment, regular medical follow-ups are necessary to monitor the recovery process, and to check for recurrence or spread of the condition.
Prevention is better than cure and some simple precautions that can be taken to help prevent melanomas during New Zealand's hotter months (September to April) include:
- Avoiding going out in the sun when UV radiation levels are at their highest (between 11am and 4pm)
- Wearing sun protective clothing when outdoors eg: hats and long-sleeved tops
- Using sunscreens with a sun protection factor (SPF) of 30 or higher when out in the sun
- Wearing UV radiation protective sunglasses
- Never allowing your skin to burn.
In addition, don't use sun beds or tanning booths,. and examine your skin regularly for new skin growths and changes in existing moles and freckles.
Further information and support
The Cancer Society of New Zealand operates a phone service staffed by specialist nurses to support patients diagnosed with cancer, as well as their friends and families.
Freephone: 0800 CANCER (0800 226 237)
Melanoma New Zealand is a charitable trust devoted to melanoma issues. Their mission is to enhance awareness, education, prevention, treatment and research of melanoma in New Zealand.
Phone: 09 4492342
Ministry of Health 2016. Cancer: New registrations and deaths 2013 (Report). Wellington: Ministry of Health. http://www.health.govt.nz/system/files/documents/publications/cancer-new-registrations-deaths-2013-nov16.pdf
Cancer Society of New Zealand (2010). Understanding Cancer: Melanoma. A guide for people with melanoma (Pamphlet). Cancer Society of New Zealand Inc, Wellington. https://auckland-northland.cancernz.org.nz/assets/Uploads/Information-section/Melanoma-Cancer.pdf
O’Toole, M.T. (Ed.) (2013). Melanoma. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis, MI: Elsevier Mosby.
Mayo Clinic (2016). Diseases and Conditions: Melanoma (Web Page). Rochester, MN: Mayo Foundation for Education and Research. http://www.mayoclinic.org/diseases-conditions/melanoma/basics/definition/con-20026009 [Accessed: 21/11/16]
Oakley, A. (2015). Melanoma – for health professionals. Hamilton: DermNet New Zealand Trust. https://www.dermnetnz.org/topics/melanomafor-health-professionals/ [Accessed: 21/11/16]
New Zealand Guidelines Group (2008). Clinical practice guidelines for the management of melanoma in Australia and New Zealand. Wellington: Ministry of Health. http://www.moh.govt.nz/NoteBook/nbbooks.nsf/0/8CDC6AE18E2D16CACC257519007591AA/$file/melanoma-guideline-nov08-v2.pdf
Smith. G. (2006) Why is New Zealand’s melanoma problem so bad? Lower Hutt: Industrial Research Limited. http://www.moh.govt.nz/NoteBook/nbbooks.nsf/0/008DB80F639A02EFCC2578C60071FAB0/$file/Why%20is%20NZs%20Melanoma%20Problem%20So%20Bad.pdf
Last Reviewed – November 2016