The summer sun is shining. But as you head outdoors to enjoy it, be mindful. More than two million Americans will be diagnosed this year with a cancer that is almost totally preventable -- skin cancer. The primary cause of skin cancer is too much sun exposure.

"If you're a cancer survivor, you should take extra precaution," says Jeffrey E. Gershenwald, M.D., professor in Surgical Oncology and co-leader of our Melanoma...