"Good Morning America" co-anchor Robin Roberts says she will begin her extended medical leave Friday.

Roberts, a 51-year-old breast-cancer survivor battling myelodysplastic syndrome, is to undergo a bone-marrow transplant. She is expected to come back to "GMA" after she recovers from the procedure; however, no specific return date has been announced.

"All this week, the program will celebrate Robin, and provide extensive reporting on her treatment, procedure and recovery process," ABC said in a news release Monday.

"Her doctor will also be interviewed about how she is preparing for the bone-marrow transplant, and explain what she can expect in the coming months. Additionally, the show will feature uplifting and powerful stories about families who have faced and overcome an MDS diagnosis."