Sally O'Neill decided to have a double mastectomy rather than "do a wait-and-see." Richard Knox/NPR hide caption

itoggle caption Richard Knox/NPR

Some images of lung cancer are clear cut. But in many others, a nodule on the screen turns out not to be cancer at all. iStockphoto.com hide caption

itoggle caption iStockphoto.com

Doreen Ramogola-Masire, an obstetrician-gynecologist in Botswana, hopes that a simple, quick screen for cervical cancer with vinegar will catch the disease early and save women's lives. Jason Beaubien/NPR hide caption

itoggle caption Jason Beaubien/NPR

Before the colonoscopy begins, it pays to ask your doctor some pointed questions. Sebastian Schroeder/iStockphoto.com hide caption

itoggle caption Sebastian Schroeder/iStockphoto.com

Cells gathered during a Pap test. Those on the left are normal, and those on the right are infected with human papillomavirus. Ed Uthman/Wikimedia Commons hide caption

itoggle caption Ed Uthman/Wikimedia Commons