Many — but not all — skin lesions are harmless

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Dear Doctor: At our family reunion up at the lake cabin, I noticed my grandfather had dozens of dark brown, rough moles on his back. Are these worrisome for skin cancer?  

Your grandfather’s “moles” are most likely harmless skin growths called seborrheic keratoses. They deserve to be evaluated and diagnosed by a dermatologist or primary care physician. If they are seborrheic

Examples of seborrheic keratosis
Examples of seborrheic keratosis

keratoses, they are not worrisome for skin cancer.

They are very common, and some estimate that they occur in 20 percent of all people. They can occur as just a single lesion but most commonly occur in large numbers. They are most commonly found on the back and chest, but they can occur anywhere except the palms and soles.

Most of the time they have a rough surface that resembles a wart. In fact, in England they call them “seborrheic warts” although they are not real warts.

Sometimes they can have a smooth, shiny surface. They start out flat but become raised over time. They can range in color from light tan to dark brown.

If you look at one closely, you can often see little white spots inside the keratosis. Another key factor to help identify them is that they often have a waxy, pasted-on look, almost like you could peel them off.

We are unsure of the exact cause, but they appear to be genetic. They do run in families. They tend to occur as one ages; in fact, the vast majority appear after age 40. They become more numerous with time.

Because they are harmless, removal is not recommended unless they are irritated by clothing or jewelry, are symptomatic (itch or hurt or bleed), or are considered unsightly to look at, in which case they can be removed for cosmetic reasons.

If a person develops dozens of seborrheic keratoses over a short period of time, they should see a doctor because this could be a rare sign of other health concerns.

Removal can easily be done by an experienced dermatologist by either freezing them (after which they peel off over about a week) or removing them surgically.

The bottom line is that these are harmless growths that occur over time. Most importantly, any spot or growth that is new or dark, changing or bleeding should be evaluated promptly by a board-certified dermatologist to make sure that the lesion is not worrisome.

Charles E. Crutchfield III, MD is a board-certified dermatologist and Clinical Professor of Dermatology at the University of Minnesota Medical School. He also has a private practice in Eagan, MN. He has been selected as one of the top 10 dermatologists in the U.S. by Black Enterprise magazine and one of the top 21 African American physicians in the U.S. by the Atlanta Post. Dr. Crutchfield is an active member of the Minnesota Association of Black Physicians, MABP.org.