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.

Questions for discussion

What is the difference between UVA and UVB?
How do we know that UV is not the cause of all skin cancers?

Transcript

Dr Elizabeth Baird
A melanoma is a cancer of the pigment cells of the skin. It’s one of the most serious cancers we see because it’s one of the leading causes of death of cancer in the 15–30 age group. Over the years, we have become aware that exposure to UV light causes sun damage. When you go out into the sunshine, you are exposed to UV light. The UVB light makes you go brown, the UVA light penetrates more deeply into the skin and destructs cellular function, which can ultimately lead to cancerous processes and irregular reproduction of the cells and a melanoma.
When you are exposed to sunshine, you can get a thermal burn where your skin will go red, and that is a sign of insult to the skin. It’s a sunburn, when your skin peels, and it’s sign of damage – a tan is a sign of damage that you've been exposed to the sunshine. And when the UV rays penetrate the skin, especially the UVA rays, which penetrate more deeply into the skin, it can cause the intracellular mechanisms to not work properly and then become cancerous.
There are other components that we do not understand. Malignant melanoma is a cancer of the pigment cells in the skin. We have pigment cells up our bottoms, and we all know that the sun doesn't shine there very much, and also the lining of the brain is the same type of embryonic tissue as the skin, so there is pigment cells in the lining of the brain. So some poor people get melanomas in areas where they do not get exposed to UV light, for example, on the meninges, which is the lining of the brain, or up the back passage – and clearly, they are not related to sunlight.

Acknowledgements
Dr Elizabeth Baird
Henry Cavillones
Ed Tarwinski
Carita Bonita
American Society of Clinical Oncology
Patrick J. Lynch
Chabacano