Food Network star Sandra Lee says she has breast cancer

 Sandra Lee attends the 2015 Housing Works Groundbreaker Awards at Metropolitan Pavilion on April 22, 2015, in New York.

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Food television star Sandra Lee says she has been diagnosed with breast cancer.

The popular lifestyle personality and live-in girlfriend of New York Gov. Andrew Cuomo divulged the news on ABC's "Good Morning America" in an interview aired Tuesday.

The 48-year-old Lee says she found out she had cancer late last month in a phone call from her doctor just after she finished a photo shoot for People magazine.

"And I walked off the set, and 20 minutes later my doctor called and told me I had breast cancer," she said. "I didn't even cry, I was stunned...You know, and that's just how fast life turns. It turns on a dime."

Lee says she has had a lumpectomy and will undergo a double mastectomy this week.

Cuomo says he expects to take some personal time to be with Lee as she handles the "trauma of her operation" and her recovery.

Lee said the cancer was detected from "a normal mammogram."

"Girls in 20s and their 30s just have to know. And I don't want women to wait. And that's why I'm talking ... If it saves one person, and makes one more person go get a mammogram, and if they're sitting down right now watching this, don't watch this TV. Go pick your phone up, and call your doctor and get your rear end in there and get a mammogram right now," she said.

Lee and Cuomo share a home in Westchester County. She said Cuomo, 57, has been "extremely supportive."