After a simple television segment led to a devastating diagnosis, ABC News anchor Amy Robach chose a double mastectomy – and a positive outlook. In her first interview since her stunning cancer diagnosis, Robach talks to PEOPLE in this week’s issue about why she regrets waiting to get checked: “A year could have made a big difference,” she says. “Then you start thinking, ‘If I had gone to get that mammogram last year, it might not have gone to my lymph nodes. I might not be looking at chemo.’”

Having reluctantly undergone an on-air mammogram on GMA on Oct. 1, Robach, 40, was stunned when she learned weeks later that she had a malignant tumor in her right breast. Regarding her decision to undergo the aggressive surgery, “I just had a visceral, immediate gut feeling that this is what I wanted to do,” she tells PEOPLE, sitting down in her Garrison, NY living room 16 days after surgery. “I said, ‘I’m young. I don’t want to live with anything hanging over my head.’” Now, she’s focused on the battle still ahead, which will include chemotherapy. “I told my kids, ‘You know Mommy is a fighter,’” she says.

With virtually no family history of breast cancer, Robach had no plans to get a mammogram. But her producers and GMA co-host Robin Roberts, herself a breast cancer survivor, urged her to get tested live for a segment. “I had a false sense of security. I run every other day. I eat well. I take care of myself,” she says. “I never imagined that this would happen.” In fact, when she initially got called back for a further scan, “I didn’t think anything of it,” she says, and waited weeks to go back for the follow up, where doctors wanted to biopsy her breast. Robach reached her husband, former Melrose Place actor and entrepreneur Andrew Shue, 46, who was out of town, just as a doctor walked in to deliver the results. She put Shue on speakerphone, “and the radiologist said, ‘Mr. Shue, are you driving?’” Robach recalls, tearing up. “Suddenly, I knew this isn’t going to be good. The next sentence out of her mouth was, ‘The tumor is malignant.’ I burst into tears hysterically.”

Shocked and devastated, Robach thought of having to break the news to her two little girls, Ava, 10, and Annalise, 7, from her marriage to ex-husband Tim McIntosh, as well as Andrew’s sons Nate, 17, Aidan, 15, and Wyatt, 10, from a previous marriage. “I don’t have a poker face. I knew I couldn’t go home and not tell them,” says Robach, who consulted a psychiatrist for guidance as Andrew and her parents, Mike and Joan Robach, flew in to be by her side. She broke the news to her kids as gently as she could: “I assured them I’m not going to die,” she says, and while there were tears, “we actually try to have a few laughs about it,” Robach explains. “I’m just trying to mirror her strength,” says Shue of his wife of three years.

Even as she faces a future of uncertainty, Robach is trying to keep a positive outlook. “They’re telling me the prognosis is good,” she says. “It’s going to be a crappy year, and then I’ll be on drugs for probably the next 10 years, and there are other issues down the road that we’re discussing and we’re dealing with. It’s about being vigilant and taking care of myself.”

While Robach and Shue admit the entire family has dealt with anger at the situation (“With any of these life-changing event, you just ask, ‘Why?’” says Shue), Robach is choosing to see the positive after so much negative. “I’m really proud of my scars,” she says of the “Frankenstein-like” incision mark under her right arm and less obvious ones under both breasts. “Look what I did, and look what I’ve been through, and I’m still here,” she says. “I can look in the mirror and see that. And remember how strong I really am.”

For more on Amy Robach, pick up PEOPLE’s 12-16-13 issue -- on newsstands everywhere now.

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