Sandra Lee will undergo a double mastectomy this week after being diagnosed with breast cancer, she announced on Good Morning America Tuesday. The 48-year-old Food Network chef and author said she was “stunned” by the news after getting what she thought would be a routine mammogram.

“I didn’t even cry, I was stunned…that’s just how fast life turns. It turns on a dime,” she told GMA anchor Robin Roberts, who's a breast cancer survivor herself.

Lee said she was diagnosed with ductal carcinoma in situ (DCIS), which is a non-invasive cancer that originates in the milk ducts and hasn't spread into the surrounding breast tissue (though it can become invasive if left untreated).

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Luckily, doctors caught the cancer early after the mammogram in March. "When the lumpectomy was done, they did not have clean margins. And so I went back to my radiologist," she told GMA. Based on her diagnosis, they recommended a course of daily radiation for six to eight weeks, or Lee could get a mastectomy.

She also went through testing for mutations in the BRCA1 and BRCA2 genes, which indicate a higher risk of breast and ovarian cancers, but thankfully the tests were negative.

Now Lee is preparing for her mastectomy, and her partner of 10 years, New York Governor Andrew Cuomo will be by her side during the surgery. “This is about her feeling secure and loved,” Gov. Cuomo told People.

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Already, Lee is pushing others to get tested early and often. She had two years to go until 50, the age at which the U.S. Preventive Services Task Force recommends starting routine screenings for breast cancer, but there’s plenty of controversy surrounding that advice.

Research on how often women should get mammograms is mixed at this point, but the concern is that early and frequent mammograms can result in false positives and unnecessary stress, or even overdiagnosis that leads to unneeded surgeries and chemotherapy.

Since the USPSTF’s recommendation in 2009, however, some doctors and organizations like the American Cancer Society have suggested starting at age 40 with annual (or even bi-yearly) mammograms.

Lee is adamant that early screening is the way to go, adding to GMA: “If I would have waited, I probably wouldn’t even be sitting here.”

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