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Melanoma skin cancer - signs, symptoms, prevention

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.  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 2000 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 which produce melanin, the pigment that causes the skin to darken when exposed to the sun. They are found in the epidermis - part of the outer layer of the skin. 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 radiation (UV) 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; 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.

Risk factors  

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 and 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 (approx 40%) and the most common site for melanomas to occur in women is the leg (approx 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
Irregular shape
Irregular colour
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 the melanoma is derived from additional examinations and tests such as: 

  • Physical examination
  • Blood tests
  • X-rays
  • 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 occuring 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 - the use of radioactive beams to destroy cancer cells
  • Immunotherapy - the use of medications that stimulate the body's immune system to fight the cancer cells
Other medications that may be used in the treatment of metastatic melanoma inclue ipilimumab and vemurafenib.

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 in order 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 include: 

  • Avoiding going out in the sun when UV 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 protective sunglasses.  
  • Never allowing your skin to burn.
  • Not using sun beds or tanning booths.

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.  The Cancer Information Service can be contacted on 0800 226 237. Information can also be obtained from the Cancer Society website -
The Melanoma Foundation of 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.  They can be contacted for information and support on 0800 463 526.  Information can also be obtained from their web site -


Cancer Society of New Zealand (2010) Understanding Cancer: Melanoma. A guide for people with melanoma. Cancer Society of New Zealand Inc, Wellington.
McCartney, R. A. and Frey, R. J. (2006) Malignant melanoma. In the Gale Encyclopaedia of Medicine (Third Edition). Jacqueline L. Longe (editor). Thompson Gale. Farmington Hills. MI.
New Zealand Dermatological Society (2012) Melanoma. In Dermnet. New Zealand Dermatological Society Inc.
New Zealand Guidelines Group (2008) Melanoma. Ministry of Health, Wellington.
Smith. G (2006) Why is New Zealand’s melanoma problem so bad? Industrial Research Limited. In, New Zealand Health Information Service.
Last Reviewed – 16 November 2012
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