BY Meagan Maisel

Monique Cohen was a healthy, busy mom of three when, in early 2011, she noticed a lump during a breast self-exam. A lumpectomy revealed it was benign, but a follow-up mammogram six months later found anotherbreast lump.

"'You have cancer.' Those are the three worst words you'll ever hear in your life," she says. "The first question you ask is, 'Why?' I did everything I possibly could to stay healthy. I exercised...