While hearing those four dreaded words changed her life, Heinz said she remained calm and did not cry.
"It was all right, funny enough partially because I know my doctor very well ... and I ask her a lot of questions. So in a sense I was being a clinical person there looking at myself," Heinz told "Good Morning America's" Robin Roberts.
Heinz's doctor explained that she had cancer in both of her breasts and would need two lumpectomies followed by targeted radiation.
But Heinz has summoned strength to push through difficult times in the past. As the wife of Sen. John Kerry ,D-Mass., she has been through countless political campaigns in which she was publicly rebuked for her occasional candor, and in 1991 her first husband, Sen. John Heinz, died in a plane crash.
Kerry, who survived prostate cancer, said he knew his wife had enough strength to overcome breast cancer.
"Her nickname among a lot of her friends is 'Doctor T.' So, she started, as she has done for other people, doing for herself or just going after the information and finding out what the options were and making some decisions pretty quickly," Kerry said.
Heinz believes in informed decisions, especially when it comes to medical procedures.
"I like to do that. You know, I do that with kids. ... in retrospect, you know, if I had been born today, I would have been a doctor," Heinz said.
Elizabeth Edwards, the wife of Kerry's former vice presidential running mate John Edwards, has also received medical advice from Heinz following her diagnosis of breast cancer.
Heinz said Kerry reached out to Elizabeth recently following the news her husband is the father of his former mistress's baby.
"I think [she is doing] all right," Heinz said of Elizabeth.