Shannen Doherty has always been transparent about the struggles she has faced. Now the actress has revealed a new struggle that she's kept out of the public eye. "It's going to come out in a matter of days or a week that I'm stage IV. So my cancer came back. And that's why I'm here," Doherty told ABC News' Amy Robach in an interview that aired Tuesday on "Good Morning America." "I don't think I've processed it. It's a bitter pill to swallow in a lot of ways."