Skin cancer
Research shows a clear link between UV and skin cancer.
The skin of an average adult has a total surface of about 1.8 square metres and a total weight of about 11 kilograms. This makes our skin our largest organ – and certainly an organ that we should look after!
Human skin
An illustration by Nick Towers, a children's book illustrator, showing the skin of a human head.
Skin has several important functions including acting like a shield to protect our body from:
physical impact such as pressure and blows
temperature impact such as heat or cold
environmental impact such as the Sun’s UV radiation, bacteria and chemicals.
Moles and melanoma
Hayley Reynolds (Auckland Bioengineering Institute) and Associate Professor Rod Dunbar (University of Auckland) explain the changes in moles that can be signs of melanoma developing.
UV and melanoma
Dr Elizabeth Baird, specialist dermatologist at Remuera Dermatology, discusses melanoma and the damaging role of UV (UVA and UVB) on the skin.
Acknowledgements:
Henry Cavillones
Ed Tarwinski
Carita Bonita
American Society of Clinical Oncology
Patrick J. Lynch
Chabacano
Skin cancer (carcinoma) is the uncontrolled division and growth of abnormal skin cells. Your skin has two main layers and several kinds of cells. The top, or outer, layer of your skin is called the epidermis. Skin cancers are classified by the type of epidermal skin cells that become cancerous.
Cross section of skin
Diagram showing a cross section of skin on the left and on the right a cross section showing the cell types.
Nature of Science
Scientists often use diagrams that are labelled to communicate detailed information. Scientists in a particular area will have a common understanding of these diagrams and the scientific language used.
Types of skin cancer
There are three common types of skin cancer:
Basal cell carcinoma develops from abnormal growth of the basal cells – the round cells in the lowest layer of the epidermis.
Squamous cell carcinoma develops in the flat scaly cells called squamous cells – found in the middle of the epidermis.
Malignant melanoma occurs in the cells called melanocytes – responsible for producing the pigment melanin, which gives your skin its colour.
Which is the worst kind of skin cancer?
Basal cell carcinoma is the most common and the least dangerous skin cancer. If it isn’t removed, it will be disfiguring, but it is not likely to metastasise (spread to other parts of the body).
Squamous cell carcinoma is easily treated if it is found early enough but can be fatal if left untreated. Melanoma is the least common but the most deadly form of cancer.
Melanoma does metastasise and spread to other organs, where it can grow rapidly and affect the ability of that organ to function properly. There is no effective treatment for melanoma that has metastasised to distant organs. It is generally incurable.
What is melanoma?
Dr Elizabeth Baird, specialist dermatologist at Remuera Dermatology, outlines what melanoma is. She explains what is meant by dissemination and why it is so important to remove melanoma before it disseminates.
Acknowledgements:
American Society of Clinical Oncology
Dr Roger Uren
What causes skin cancer?
Research has shown that these skin cancers generally develop because of over-exposure to UV radiation (from the Sun or from sunlamps or tanning beds). Each time your unprotected skin is exposed to UV, the UV causes changes to take place in the structure of the genes and in the behaviour of the cells.
Risk factors for melanoma
Dr Elizabeth Baird, specialist dermatologist at Remuera Dermatology, outlines the relationship between UV, melanocytes in the skin, tanning and melanoma risk. She discusses the risk factors of skin type and family history in the development of melanoma.
Acknowledgements:
TVNZ Television Archive
Normally, cells grow and multiply in an orderly way. However, damaged genes can cause cells to behave abnormally. These abnormal cells may grow into a lump (a tumour). These tumours will either be benign (not cancerous) or malignant (cancerous). Benign tumours can grow, but they do not spread to other parts of the body (metastasise).
Skin cancer statistics in New Zealand
Dr Elizabeth Baird, specialist dermatologist at Remuera Dermatology, gives information on the risks of melanoma and other skin cancers in New Zealand compared with elsewhere.
Acknowledgements:
Arun Kulshreshtha
Josef Wienand
At first, a malignant tumour will stay confined to its original site. (This is called carcinoma in situ.) However, if the cells are not treated quickly, they may spread into surrounding tissue and to other parts of the body. (This is called malignant or invasive cancer.) When these cancer cells reach another part of the body, they may continue to grow and form another tumour. This is called a secondary cancer (or a metastasis).
How is skin cancer treated?
Diagnosing melanoma
Dr Elizabeth Baird, specialist dermatologist at Remuera Dermatology, outlines the procedure used to diagnose and remove a melanoma.
Different types of cancer require different kinds of treatment. These include:
surgical removal (the most common treatment)
chemotherapy
radiation therapy
immunotherapy
hormone therapy.
What is lymphoscinitigraphy?
Associate Professor Rod Dunbar (University of Auckland) explains the procedure of lymphoscintigraphy as a technique to determine the first lymph nodes melanoma will spread to.
Acknowledgements:
TVNZ TELEVISION ARCHIVE
Dr Roger Uren
Once a cancer has developed, the outlook depends on a number of factors, including the type of cancer and how quickly it is diagnosed and treated.
Related content
These related articles explain why New Zealand skin cancer rates are so high, some of the risk factors and how skin cancer is diagnosed and treated.
Activity idea
For those interested in protection from UV, see The face of melanoma – an activity that looks at lifestyle factors that contribute to skin cancer.
Useful links
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.
The Cancer Society of New Zealand is the leading organisation dedicated to reducing the incidence of cancer and ensuring the best cancer care for everyone in New Zealand.
Melanoma New Zealand is a charity dedicated to preventing avoidable deaths and suffering from melanoma.
This Skin Cancer Foundation web page looks at skin types and at risk groups.
This HealthMatch article, Top 20 skin cancer hot spots in the world and why they're on the list, explores the roles that personal, cultural, and global habits play in rates of skin cancer and what we can do to change them.
