On Nov. 11, the 40-year-old correspondent revealed that she was diagnosed with breast cancer after getting a mammogram live on "Good Morning America." Robach has since had a bilateral mastectomy, followed by reconstructive surgery.
She says it was during her mastectomy on Nov. 14, that her surgeon found a "second undetected malignant tumor".
"No MRI, no mammogram, no sonogram had found it ... it was only through the mastectomy that she discovered it," Robach said in an email, adding that the cancer spread to a lymph node.
Despite further treatment, the television journalist remains upbeat and says she can't wait to get back to work.
On Friday, Robach reached out to her ABC colleagues and thanked them for their love and support through such a difficult time:
"It may be cold and gloomy outside today but it is warm and sunny in my world. This message is long and overdue ... it has been weighing heavily on me how much gratitude I owe each and every one of you. The unbelievable outpouring of support from ABC began from the first moment I received my diagnosis. Phone calls, emails, cards, flowers, blankets, care packages, food, pajamas, slippers, help with insurance, medical advice ... The list goes on and on ... It was truly overwhelming how many of you thought of everything anyone could possibly want or need during a time of medical crisis. It brought so many tears of joy to my eyes and warmed my heart more than you'll every know to see what my ABC family did for me and for my entire family ...
Your support and love has made this all an experience that has given me the strength to fight the fear and hopefully help others do the same in the days/weeks/years to come!"
Robach was a frequent fill-in on ABC's morning show while Robin Roberts was fighting a serious blood and bone marrow disease. She says she expects to come back to work the Monday after Thanksgiving.
ABC News contributed to this report.