Moles and Sun: A Dangerous Combination

Benign moles (or nevi) are so common that pretty much every human being on earth has them. In the language of medicine, “benign” means noncancerous. However, exposure to dangerous ultraviolet (UV) rays from our sun can create mutations on moles that cause nevi to turn from safely benign, to dangerously malignant (cancerous). UV rays even often promote a common mole’s formation to begin with.

In a report cited within an article posted by the Helen Diller Family Comprehensive Cancer Center, researchers in California have discovered a way to determine the direction moles take as they transform from skin lesions (“precursors”) to reaching their fully malignant, potentially fatal, forms.

This easy to remember chart shows the progression to melanoma upon UV exposure:

Normal mole (1 mutation) —-> Atypical mole (several mutations) ——> Melanoma (many mutations).

It was the data gathered by this group of scientists that confirmed the negative impact UV rays have on skin by initiating the growth of moles, as well as turning them cancerous. It also confirmed the existence of “intermediate lesions”, which are lesions whose benign or malignant status is not easily determined. The latter discovery will be greatly beneficial to dermatologists when choosing the treatment for their melanoma patients.

So, what does all of this mean to those of us who are non-medical laypersons? That has been neatly summarized by the words of Dr. Boris Bastian; the report’s senior author:

“A lot of melanomas have been sequenced at this point, and while it’s clear they carry UV-induced mutations, no one knew when they occurred…This study shows that they occur in benign moles, in the melanoma that arises from these moles, and in intermediate lesions. UV both initiates and causes the progression of melanoma, so exposing even benign moles to the sun is dangerous.”

Just because a mole is benign doesn’t mean it will stay that way. It’s very important to always take the appropriate skin protection precautions whenever we’re exposed to the sun.

*Additional information sources: University of California San Francisco, Helen Diller Family Comprehensive Cancer Center

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