ABC News reporter Amy Robach has breast cancer! The TV journalist learned about it through an on-air mammogram, which was held on Good Morning America's show as part of the breast cancer awareness month.

The 40-year old Robach confessed her diagnosis on the "Good Morning America" show last Monday. She also revealed that she will be undergoing a double mastectomy on Thursday.

"I've decided to be very aggressive," Robach told Robin Roberts, who was a cancer survivor herself, on the show.

Robach wrote in a blog that she is being asked to take a mammogram by the producer of the show, for which she considered that it would be "virtually impossible" that she had cancer at that time.

"That day, when I was asked to do something I really didn't want to do, something I had put off for more than a year, I had no way of knowing that I was in a life-or-death situation," she penned.

Robach eventually agreed after her bosses pointed out to her that "the age women should start getting mammograms" so she took the on-air mammogram on October 1, after a few weeks the results came and she found  out that she has breast cancer.

"Between flying all over the world for work, and running around with my kids to school and ballet and gymnastics like so many women, I just kept putting it off," she said to Roberts.

Thankfully, she learned about the cancer early and is now all geared up to fight the battle.

 "Only then will I know more about what that fight will fully entail, but I am mentally and physically as prepared as anyone can be in this situation," she wrote.

Robach was thankful to her colleagues that they have pushed her to take the assignment to support the Breast Cancer Awareness Month.

"Thank God you did," Robach told Roberts. "I had cancer the whole time we were sitting in that office, and I said, 'I don't have any connection to that disease.' "

The news reporter will be taking an indefinite leave of absence from her show, spokesperson of ABC announced.

She will be battling with an illness that will lead her to a "tornado of tests," where she will find out about the questions  that are yet to be answered.

"There's a lot you don't know until you have the surgery," she said on the show on Monday.

"I don't know about chemo. I don't know what stage I am. I don't know if it has spread. So we'll find out those things in the weeks to come."

Robach's husband "Melrose Place' hunk Andrew Shue, who was on a business meeting during her diagnosis, immediately flew to New York when he heard about the news. The couple has five children from their previous marriages. Robach has two daughters while Shue has three sons.