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The Informed Parent

When Are Moles a Concern?

by Louis P. Theriot, M.D., F.A.A.P.
Published on Jan. 24, 2011

Carlos is a sophomore in high school and a varsity cross-country runner. Mom brought him in because of a cough he hasn’t been able to shake for the past couple of weeks. After getting the history Carlos sat on the examining table and took off his shirt. As I was listening to his back mom stood up, put on her glasses and came closer to examine his back.

“I don’t often get to look at his skin up close,” she said in a pensive tone. “But look at these moles on his back. Should I be concerned about these?” I asked if there was a family history of skin cancer, and she said that the grandfather had melanoma. At this point I had Carlos undress in order for me to completely examine his skin in greater detail.

Moles, or more correctly pigmented nevi, are very common. They are clusters of melanocytes which are the cells that give the skin pigment. There are two major classifications of pigmented nevi: congenital or acquired.

CONGENITA NEVI occur in about 1% of all newborns. They may be small congenital nevi which are less than 2 cm in diameter or giant congenital nevi which are greater than 20 cm in diameter—-over 8 inches. Or they may be intermediate congenital nevi which fall in-between the two others.

Small congenital nevi have a predilection to occur on the lower trunk, upper back, shoulders, chest or proximal limbs. These are considered relatively harmless and rarely degenerate into a cancerous condition. They should be followed clinically.

Giant congenital nevi, on the other hand, are much more concerning because they have the propensity to become cancerous and should be seen by a specialist as early as possible. These tend to occur most often on the posterior trunk, and less commonly on the head and extremities. These are quite large and unsightly, and may have tufts of hair growing from them. They are not very common, occurring in around 1 in 20,000 individuals. However, 5 - 10% of these become malignant melanomas. About 50% of melanomas that arise from giant congenital nevi do so in the first five years of life!

ACQUIRED NEVI are very common and for the most part benign. These are the so- called common moles. They are flat and uniform in color, and have sharp and distinct borders. They may be light in color but most tend to be dark brown. Most moles tend to become darker during the teen years as the youngster goes through puberty. Acquired nevi tend to gradually increase in number during childhood, sharply increase during the adolescent years, and then plateau during the third and fourth decades. After that they dramatically decrease. The mean number of moles in adults is 25 to 35. It is also reported that the greater the number of moles, the greater the likelihood of melanoma. So, if one has more than 30 moles, it is wise to have this followed closely.

Moles can undergo changes that make them at risk to become cancerous, or pre-cancerous. We refer to these changes as DYSPLASTIC CHANGES. These moles would now have 1) irregular and asymmetric borders, 2) undergone color changes within (such as a speckled appearance or more than one solid color within), 3) small “satellite” mole-like growths emanating from the original mole which is often referred to as ”mushrooming”, 4) grown rapidly in size instead of growing along with the individual, 5) grown to a size with a diameter greater than 6mm which is the size of a standard pencil eraser, or 6) become itchy or bleeding when scratched. These are the telltale signs that the mole MUST be seen by a dermatologist.

Getting back to Carlos, none of the moles he had appeared dysplastic. It is of interest that during cross-country and track season he rarely wears a shirt when working out. He had a large number of dark moles on his back that I feel were darkened by the direct sun exposure, but it’s hard to say if these were caused by the sun. Nonetheless, I counted 22 moles, most of which were on his back. None of them were dysplastic or particularly concerning. But I told mom that I wanted him to see a dermatologist in order to establish a baseline. The dermatologist will document the moles, will measure them and take pictures so that if there are any subtle changes from year-to-year, it will be well documented. Carlos’ mom nodded in agreement and whispered to me so that he wouldn’t hear, “His grandfather died of malignant melanoma at a young age.”

I gave her the card of the dermatologist when she said she thought she would have her other children seen as well. Just then Carlos looked at both of us and asked, “Hey, what about my cough…?”

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