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Skin Cancer

Our guest expert in July 2010, was Dr. An-Wen Chan, dermatologist and Mohs surgeon at Women’s College Hospital, assistant professor of dermatology at the University of Toronto and clinical epidemiologist at Women’s College Research Institute.

Dr. Chan completed a doctorate in clinical epidemiology as a Rhodes Scholar at Oxford University, U.K. and had further fellowship training in dermatologic surgery and skin cancer at the Mayo Clinic in Rochester, U.S.A. His clinical practice focuses on the treatment of high-risk skin cancers, primarily involving the face, or in immunosuppressed organ transplant patients. His research interests include the epidemiology and management of high-risk skin cancer in solid organ transplant patients, as well as issues of transparency and biases in randomized trials.

Dr. Chan is a former special advisor for the Randomized Controlled Trials Unit at the Canadian Institutes of Health Research, and was seconded to the Department of Research Policy and Cooperation at the World Health Organization in Geneva to help co-ordinate the WHO International Clinical Trials Registry Platform. He currently chairs the international SPIRIT initiative to develop standard guidance for randomized trial protocols.

Here are his answers on Skin Cancer.

Q: Are dark-skinned people less prone to skin cancers from sun damage? Is this true even if they have lived in the Caribbean for a number of years and were much more exposed to the sun?

A: The darker the skin colour, the lower the risk of skin cancer because of the additional protective pigment that is present. For the same amount of sun exposure, darker-skinned people are much less prone to develop sun damage and skin cancer. However, more sun exposure increases the risk of skin cancer no matter what the skin colour.Darker skin just means that you are starting at a lower baseline risk.


Q: As I age I have noticed more marks on my skin. Is it normal to get more skin spots and blotches as one gets older? Could you give some pointers as to what’s normal and what needs attention – such as warning signs of cancerous cells, including basal cell cancer?

A: There are many spots and blotches that appear with age. These can range from harmless (benign) to dangerous (cancerous) lesions, and are mainly caused by sun damage over the years. General warning signs that suggest skin cancer include new spots that are changing (e.g. in size, shape, or colour), bleeding with minimal trauma, or not healing normally. For detecting melanoma, one of the most dangerous kinds of skin cancer, we recommend that patients look for the ABCDE signs:

Asymmetry (one half different from the other half);
irregular Border (not smooth);
>1 Colour present;
Diameter > 6mm; and
Evolving (e.g. changing in size, shape, colour).

But the bottom line is to have your doctor check any skin spot that concerns you.


Q: Are tanning beds safe if used in moderation?

A: No.There is no such thing as a safe tan (except for fake tans). Tanning is a sign of skin damage, which predisposes to skin cancer.


Q: Who is most at risk for getting skin cancer?

A: Common risk factors include fair skin, red or blonde hair, blue or green eyes, and a tendency to burn rather than tan after sun exposure. Individuals who are immunosuppressed or have certain rare genetic diseases are also at higher risk. While skin cancer generally affects more males and more elderly people, we commonly see skin cancer in younger as well as female patients. In fact, the incidence of skin cancer is increasing the fastest in women under the age of 40 years old.


Q: What exactly is Mohs surgery?

A: Mohs surgery is a specialized technique for removing high-risk skin cancers in areas such as the face. It involves cutting out the tumour and testing the tissue under the microscope during the procedure to make sure that 100% of the roots and edges of the cancer have been removed. If  any of the tumour remains then more tissue is removed at the precise location as seen under the microscope. This allows the Mohs surgeon to leave as much of the normal skin as possible and only cut out the problem areas to ensure that the tumour is fully removed. The main advantages of Mohs surgery are higher cure rates and smaller surgical scars.


Q: It has been stated that we can have 10 minutes of direct unprotected exposure to sunlight every day to get our vitamin D. Is that really OK? Does this apply to people who already have a type of skin cancer?

A: It is true that we only need short exposure to the sun to produce vitamin D, and any extra time doesn’t help produce more. But for those at risk of sun-related problems there are other more effective ways to ensure your vitamin D levels are healthy. Vitamin D is readily available as an oral supplement and in a variety of foods. There is no need to be exposed to a known cancer-causing agent like the sun when vitamin D can simply be taken by mouth. In particular, people who have already had a skin cancer are at much higher risk of getting another one, so sun avoidance is even more important.


Q: I have a mole that I had a doctor take a look at. She said not to worry about it. However, the mole is sometimes itchy and sometimes there is a quick pain going through it. Are those signs that I should show it to my doctor again?

A: It is hard to know whether a mole is dangerous based on symptoms alone. Skin examination is a key part of diagnosis, and I would suggest having it checked by a dermatologist if you are concerned.


Q: I live in Central America and am exposed to the intense sun daily, and surf in the ocean. I am fair-skinned and blonde. What sunscreen would you recommend that I use? Thanks so much for your help.

A: I would recommend a sunscreen that is at least SPF 30 or higher and has broad-spectrum protection against both ultraviolet A (UVA) and UVB rays. In addition to sunscreen, it would be important to wear protective clothing (e.g. long sleeves, hat, and long pants) and avoid direct sun exposure during the peak times of 10 a.m.-4 p.m. There are several types of UV-protective clothing available to wear while surfing or swimming. In addition, the Canadian Dermatology Website has some tips on sun safety related to your question.


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