Moles are common, but how do you know if a growth is melanoma, the most dangerous type of skin cancer?
Everyone has at least one mole (naevus), but some people could have as many as 500 or even 600, although these are usually seen in Caucasians. It is unusual for Asians, who typically have less than 100, to have such a large number of moles. What is usual, however, is for the average person to have anywhere from 10 to 40 moles on his or her body by adulthood.
Newer studies — which included only Caucasian patients — have suggested that more than 11 moles on the right arm indicate a higher-than-average risk of skin cancer or melanoma. People with more than 11 moles on this arm are more likely to have more than 100 on their body in total, meaning they are at a higher risk of developing melanoma. Having more than 100 moles indicates five times the normal risk.
The study by King’s College, published in the British Journal of Dermatology in 2015, used data from 3,594 female twins in the United Kingdom. A repeated exercise on about 400 men and women with melanoma gave researchers this quick way to assess the risk of skin cancer. As Caucasian patients with susceptibility to melanoma often have a large number of moles, mole count is a very important clinical marker of increased melanoma risk.
However, total body skin examinations with mole checks are rarely performed in general practice as these are time-consuming. The ability to estimate total body mole count quickly by counting moles on one arm could be useful in assessing melanoma risk in primary care. However, as it is not common for Asians to have more than 100 moles, one will have to be cautious in extending its applicability to our local population.
Moles that develop at birth or within 6 months of life are known as congenital moles. The rest are acquired due to accumulated factors such as sun exposure, and most of these appear during the first 30 years of a person’s life.
Moles can occur anywhere on the body — even the scalp — due to a collection of pigment-producing cells in the skin known as melanocytes. Moles vary greatly in appearance, from brown or black to lightly pigmented or flesh-coloured.
These benign growths are usually small, measuring less than five millimetres, and flat when they first appear. With age, they can become raised and dome-shaped. But unless these spots happen to be of an embarrassing size and location, most people are inclined to leave them alone.
Occasionally, however, a mole’s change in appearance can become a cause for concern, says Dr Chen Qiping, Associate Consultant at the National Skin Centre (NSC),” especially if they develop an irregular border, change colour or suddenly increase in size”.
The good news is melanomas are still relatively rare in Singapore. The incidence rate of melanoma is 0.3-0.5 per 100,000 persons per year, and it accounts for more than 0.5 per cent of all skin cancers in Singapore.
In contrast, in Australia, which has the highest melanoma rate in the world, one in 14 men and one in 24 women will be diagnosed with melanoma in their life. Melanoma accounts for two percent of all skin cancers in Australia.
The relatively lower rate of melanomas in Singapore is because the darker your skin type, the more melanin and natural protection you have against the sun’s harmful UV rays. However, as melanomas are the deadliest of all skin cancers, due attention should be given to it.
Dr Tan Wee Ping, Head of Skin Cancer Clinic at NSC, recommends regular self-examination of your skin. “All areas of the skin should be inspected, including the hands and feet, genital areas and nails. One important point to note is that melanoma and other skin cancers are usually asymptomatic till very late stages. Some patients who present in late stages have told us that they had brushed off their skin growth as innocuous due to the lack of symptoms,” she says.
Dr Chen suggests using mirrors for areas that are hard to see and taking photos of your moles to keep track of their size and appearance.
”Any persistent new or changing mole or skin growth requires medical attention. Melanoma can occur anywhere on the skin. A local study has found that the most common type of melanoma in our local population is the acral lentiginous melanoma that occurs over the hands, feet or even under the nails,” she says.
Some people are concerned about hair growing out of a mole, but the hair is a good sign that your hair follicles are intact and healthy. You can snip away the unsightly hair, but do not pluck them as doing so can irritate the mole.
Related: Skin Diseases of the Scalp
Since the leading cause of skin cancers like melanoma is chronic or intense exposure to harmful UV rays, the most effective precaution you can take is to limit sun exposure. Dr Chen advises the following:
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This article was last reviewed on
22 Nov 2023
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