Sun damage: The ghost that returns decades later

I went to the dermatologist today to have the first of two skin cancers removed — one on my face, the other on my neck. As she worked, I asked whether I should finally spring for tinted windows in my car. She smiled gently and said, “You can, but the roots of these growths go back more than 20 years.”

That sentence landed like a rock. Twenty years? I had thought of all the times I had driven lately with the Florida sun blazing through my window or walked the dog “just for a minute” without a hat or sunscreen. The damage, my dermatologist explained, was already baked in.

The long shadow of the...