Mutations that drive cancer lurk in healthy skin

Changes not so rare — nor a sign of imminent tumor growth

eyelid

EYE-OPENER  Normal skin is a patchwork of cells, many of which carry cancer-driving mutations, a new study finds. In a representation of normal skin, colors indicate the mutated genes and circles reflect the size of skin patches from healthy eyelids carrying the mutation.

I. Martincorena et al/Science 2015, I. Martincorena

By late middle age, about a quarter of skin cells carry cancer-driving mutations caused by exposure to sunlight — and it’s perfectly normal.