As a young man, John spent every summer afternoon at the pool for many years. As he approached the age of 50, his skin was quite wrinkled, and he discovered some suspicious growths on his face. He...

As a young man, John spent every summer afternoon at the
pool for many years. As he approached the age of 50, his
skin was quite wrinkled, and he discovered some suspicious
growths on his face. He visited a dermatologist, who removed
these growths. What were the growths, and what probably
caused them?