"I knew the minute the doctor came in the door. I could tell by her demeanor. 'You have breast cancer.' The words are so surreal," she told Roberts.
Lunden's treatment will include a lumpectomy, chemotherapy and radiation, but she is expected to make a full recovery.
"I have covered many stories about breast cancer over the years but I never actually thought this would happen to me," Lunden said in a statement. "I have shaped my career around health & wellness advocacy so it seemed natural to share my story. I've started chemotherapy and while I don't know how I’ll look and feel down the road, I am assuming the best because that is how I live my life."
She also tweeted her thanks to for the swift support she's already received..