VIDEO: Joan Lunden Shares Breast Cancer Diagnosis on GMA

Longtime GOOD MORNING AMERICA co-host Joan Lunden stopped by this morning's show to discuss her recent breast cancer diagnosis with GMA anchor Robin Roberts. Watch the appearance below.

The journalist also revealed the news of her diagnosis simultaneously on Facebook, posting, "I have covered many stories about breast cancer over the years but I never actually thought this would happen to me."

She continues, "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 wrote.

Roberts and "GMA" news anchor, Amy Robach, have also recently been treated for breast cancer.

Lunden's treatment will include a lumpectomy, chemotherapy and radiation. Thankfully, she is expected to make a full recovery.

VIDEO: Joan Lunden Shares Breast Cancer Diagnosis on GMA