When Tom Brokaw was diagnosed with multiple myeloma in 2013, “I didn't know what I was in for,” he says.

In a special edition of NBC's Dateline this week, the 75-year-old opened up about his emotional cancer fight, and his powerful new memoir, "A Lucky Life, Interrupted," which is being released May 12.

“I'm a guy who's had great good fortune in his life,” Brokaw said. “And everything has kind of gone in my direction. And so I couldn't imagine that I was going to go through the ordeal that it turned out to be.”

The former news anchor was diagnosed with the treatable but incurable blood cancer in August 2013. After months of specialized treatment at the Mayo Clinic, he is currently in remission.