Melanoma
Melanoma is the most serious form of skin cancer. It begins in the melanocyte cells of the skin, which are found in the bottom layer of the skin’s epidermis, in the middle layer of the eye and in the meninges (membranes around the brain), among other places in the human body. They produce a brown-black pigment called melanin that determines skin, hair and eye colouring. Melanin also helps protect against the damaging rays of the sun.
Cross section of melanocytes
A cross section diagram of the skin showing the epidermis, dermis, and melanocytes spreading.
Melanocytes often multiply to form concentrated clusters that appear on the skin surface as small, dark, flat, or dome-shaped spots – usually harmless moles or liver spots. This happens particularly as people age. If the melanocytes multiply in a controlled and contained way, the mole is harmless (benign).
However, sometimes, the melanocytes multiply out of control and become a malignant and life-threatening melanoma. At first, the melanoma cells just grow sideways, and so are restricted to the epidermis and to the top layers of the dermis of the skin. However, if they start to grow downwards into the dermis, the cancer will come into contact with lymph vessels and can spread through these vessels to distant sites (this spreading is called metastasis), so it is very important to remove a melanoma while it is still thin, before it penetrates to these deeper layers of the skin.
Some types of melanoma develop and thicken very quickly (over a few weeks), while others can take months or even years to develop.
UV, melanocytes and melanoma
Dr Hayley Reynolds and Professor Rod Dunbar explain the effect of UV on melanocytes.
Select here to view video transcript and copyright information.
The most common areas for melanoma are those exposed to the sun, but melanoma can develop in any skin type cells in the body, even areas not exposed to the sun (such as the lining of the brain, the back of the eye, underneath fingernails and toenails, or on the soles of the feet).
Melanoma on foot
A small melanoma on a foot.
How common is melanoma?
Unfortunately, New Zealand has one of the highest incidence and death rates from melanoma in the world, in 2020 we had the world's highest death rate from melanoma. In New Zealand and Australia, our incidence of melanoma is about four times as high as in Canada, the USA and the United Kingdom. In 2004 there were 1,896 melanoma registrations and 249 deaths from melanoma, by 2020 the death rate had increased to over 350 each year.
Skin cancer statistics in New Zealand
Dr Elizabeth Baird gives information on the risks of melanoma and other skin cancers in New Zealand compared with elsewhere.
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How is melanoma identified?
Melanomas usually appear as a changed mole or freckle, so if any mole or freckle changes, get it checked out. One simple way to remember the signs and symptoms of melanoma is the mnemonic ABCDE:
Asymmetrical – if you rule a line through the middle of the mole, freckle or lesion, it is not the same on both sides. Normal moles are usually quite symmetrical.
Border – the border is irregular or not well defined.
Colour – melanomas usually have multiple colours or are dark (or have no colour at all).
Diameter – moles greater than 6 mm are more likely to be melanomas than smaller moles.
Evolution – any change in a mole or freckle should be looked at.
Melanoma check chart
The Melanoma ABCDE detection system is useful for tool for checking for possible melanomas.
Some charts also include an 'F' for 'firm to touch' or 'funny looking' and a 'G' for growth.
It is not foolproof because some melanomas do not have any of these more common characteristics. If you have any doubts about a change in your skin you should always see a doctor.
Gajera, Himanshu & Zaveri, Mukesh & Nayak, Deepak. (2022). Patch‐based local deep feature extraction for automated skin cancer classification. International Journal of Imaging Systems and Technology. 32. 10.1002/ima.22729.
Moles that develop later in life should also be looked at quickly. Most benign moles (non-malignant) have been present since childhood.
Moles and melanoma
Hayley Reynolds and Professor Rod Dunbar explain the changes in moles that can be signs of melanoma developing.
Select here to view video transcript and copyright information.
Nature of science
Scientists are always trying to find answers to those questions that have not yet been answered. Melanoma is an example of a disease where survival rates have lifted as new treatments have been developed. Prior to the 2000s, advanced melanoma was untreatable.
Treatment
One of the best ways to protect against the dangers of melanoma is to catch it before it’s too late. Melanoma has a high cure rate if it is caught early on. As with most cancers, early detection results in better outcomes.
Diagnosing melanoma
Dr Elizabeth Baird outlines the procedure used to remove and diagnose a melanoma.
Select here to view video transcript and copyright information.
Like other types of skin cancer, the most effective treatment is surgical removal. In fact, despite many years of intensive research, surgical removal of melanoma before it is 1 mm thick is the only effective cure. The thinner the melanoma, the less it has burrowed into the skin and the better the outcome. For example, thinner melanomas can often be treated with surgery alone. Once the melanoma has spread (metastasised), treatments need to include chemotherapy and immunotherapy. The five-year survival rate for melanoma that has spread, has dramatically improved from less than 10% in 2008 to around 55% in 2024. This because of new drug treatments – however, not all drug treatments are publicly funded in New Zealand.
Related content
Find out more about skin cancer, why New Zealand skin cancer rates are so high, some of the risk factors and how skin cancer is diagnosed and treated.
For more learning around UV light see You, me and UV – introduction.
For a real world research angle – take a look at the early research of Dr Hayley Reynolds on a Melanoma spread pattern model.
Student activities
The face of melanoma is an activity that looks at lifestyle factors that contribute to skin cancer.
To tie in sun safety with skin cancer learning – take a look at the activities Investigating sunscreens, Investigating UV intensity and UV bead items.
Useful links
Melanoma New Zealand is a charity dedicated to preventing avoidable deaths and suffering from melanoma.
The SunSmart website is designed for students, teachers, schools and parents. It has information about UV, shade, hats, sunscreen, skin cancer and sun protection, as well as cross-curricula resources for teachers in the SunSmart Schools section.
Visit the UV exposure section from the Environmental Health Indicators Programme, Massey University. It includes statistics about UV exposure in Aotearoa New Zealand, and how it can affect our health.
