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Five years ago, Robin Roberts overcame breast cancer after a very public battle with the disease, and on this morning's GMA, the anchor announced she is currently facing a new health complication.

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"Sometimes treatment from cancer can lead to other serious medical issues and that's what I'm facing right now," Roberts said through tears as she revealed she's now suffering from Myelodysplastic Syndrome -- a rare blood disorder that affects the bone marrow.

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"The reason I am sharing this with everybody right now is because later today I begin pre-treatment," she said, adding that a tube would be added to her arm this afternoon so she can more easily give blood and receive drugs. "I didn't want you to be concerned if you saw it there tomorrow."

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But her prognosis is positive as Roberts revealed, "My big sister is a virtually perfect match and she is going to be my donor. Doctors tell me that is going to be a tremendous help in me beating this."

And the positive attitude the 51-year-old adopted during her breast cancer treatment is still alive and well. "Five years ago I beat breast cancer, and I've always been a fighter. It's about focusing on the fight, not the fright [and] I am going to beat this," Roberts declared.