Explainer

Sun spots on skin: the four-question sort that tells you which of four things you actually have

"Sun spot" is not a diagnosis, it is a lay word that covers at least four different things on sun exposed skin, and one of them is a precancer that people usually feel before they can see it. Here is a four-question sort you can run with a fingertip and a calendar, and the awkward fact that no study has ever counted how often a self-described sun spot turns out to be each one.