Another skin-cancer myth — busted

I know many dermatologists who carefully count up the total number of moles their patients have. They say if you have lots of these growths, you have a higher risk of developing melanoma skin cancer.

It turns out, they are wrong. Not only that — they have it completely backwards. And there’s no need to perform this painstaking procedure. In fact, recent research suggests that if you have lots of moles, you actually have a much lower risk of developing melanoma than someone with very few moles. And if you do happen to get melanoma, the presence of multiple moles may indicate that the cancer will behave less aggressively. I’ll tell you more about this interesting new discovery in just a moment. But first, let’s back up a step…

As I often remind you, melanoma is the one and only deadly form of skin cancer. It can and does kill. But melanomas make up just 9 percent of all skin growths classified as “cancerous.”

Melanoma comes from melanocyte skin cells, the pigmented cells that allow our skin to turn tan when exposed to sunlight. They make and release melanin, which darkens the skin. People of color, with naturally dark skin, have more melanocytes in their skin.

Many doctors obsess unnecessarily on skin moles, technically called “pigmented nevi,” because they have high concentrations of melanocytes. They assumed we need to carefully monitor these growths because they expected malignant melanoma to arise from these sites.

But new research says we’ve been looking in all the wrong places.

Fewer moles linked to higher melanoma risk

In a new study published in JAMA Dermatology, researchers studied 566 patients at two academic medical centers and an affiliated VA hospital. Doctors surveyed the patients from 2006 to 2009, within three months of having a melanoma skin tumor biopsy. They measured thickness of the tumors. Typically, the thicker the tumor, the more aggressive the cancer. They also counted the number of moles on the skin.

The researchers divided the patients into three groups. Patients in the first group had zero to 19 moles. The second group 20 to 50 moles. And the third group had more than 50 moles each.

The researchers also evaluated the moles as to whether they appeared “atypical,” which is thought to increase the risk of developing melanoma.

Strikingly, the majority of patients with melanoma skin cancer were actually in the low “0 to 19” mole category. And none of the few moles they did have were characterized as “atypical.” All their moles were just average skin moles. Also, the older the patient with melanoma, the fewer moles they had.

I also found it interesting that people under 60 years old who had greater numbers of moles — in the more than 50 moles category — had thinner melanoma cancers, which are typically less aggressive cancers. But in patients younger than 60 years, the presence of more than five atypical moles was associated with thicker melanoma cancers.

So in this study, melanoma skin cancer was more commonly diagnosed in people with fewer moles, compared to those with a higher mole count. And in younger and middle-aged patients who have a lot of moles, and do get melanoma skin cancer, the cancer is thinner and therefore less aggressive or dangerous.

What does it all mean for you?

So — having more moles may actually protect you against getting melanoma skin cancer. And if you get melanoma, chances are it may be a thinner, less aggressive cancer.

Remember — there are melanocytes in the skin all over the body. Yes, there is a higher concentration of melanocytes in skin moles. But moles cover only a very small percentage of the skin, even in people with lots of them.

Most of the melanocytes are located elsewhere in the skin. So it stands to reason most of the melanomas will arise from melanocytes that don’t happen to be located in moles.

While the researchers didn’t answer why having more moles appears to protect people from melanoma, this new study did put another myth about skin cancer to rest.

Of course, you can’t do much about how many moles you have on your body. But there is a simple step you can take that can help reduce your risk of skin (and most other) cancers: Spend more time in the sun.

This advice is also contrary to what you typically hear from dermatologists. And indeed, other studies link melanoma risk with over-exposure to the sun and sunburn during adolescence and young adulthood. (That’s one reason young people shouldn’t frequent tanning booths. Fortunately, the FDA has recently taken steps to regulate tanning bed use more stringently.)

But, as you get into middle- and old-age, don’t be afraid to go out in the sun. Spending more time in the sun will help raise your vitamin D levels, which lowers your risk of skin cancer, prostate cancer (as I reported last week), and most other cancers.


“Total Nevi, Atypical Nevi, and Melanoma Thickness: : An Analysis of 566 Patients at 2 US Centers,” JAMA Dermatology, ( 3/2/2016