Former "Good Morning America" co-host Joan Lunden is sharing some difficult personal news. The 63-year-old broadcast vet returned to her former morning show home Tuesday to reveal she's been diagnosed with breast cancer during an interview with current "GMA" co-host and cancer survivor Robin Roberts.

Lunden described her cancer as "the aggressive kind" that showed up during an ultrasound instead of a mammogram. Optimistic about her prognosis, Lunden says she will soon begin treatments to battle the cancer, including chemotherapy.

Lunden co-hosted "GMA" from 1980 until 1997.

[Metro Networks]