Joan Lunden, former "Good Morning America" host, has breast cancer

Former "Good Morning America" host Joan Lunden returned to the morning show she used to co-anchor on Tuesday to reveal she has breast cancer.

The 63-year-old journalist disclosed her diagnosis on the ABC morning show, which she co-anchored from 1980 through 1997. She spoke with "GMA" host Robin Roberts, who has also been treated for breast cancer recently, as has "GMA" co-host Amy Robach.

Lunden said her treatment will include surgery and radiation. She said she's already started chemotherapy.

She said after the initial shock of the diagnosis, she resolved to learn everything she can about the illness and go into what she called "warrior mode." She said she expects to make a full recovery.

On her Facebook page, Lunden added, "My hope is to get the message out that no matter what type of cancer you might have, early detection is so important. We can't be afraid to talk about it and share our stories with one another."

Lunden is now a health and wellness advocate. She has written eight books.