The news came as she left a shoot for PEOPLE's Most Beautiful issue in March. "Life can turn on a dime," she tells PEOPLE, having first revealed the news on Good Morning America Tuesday.
Lee – who has started to document her thoughts and medical appointments in a no-holds barred video diary – was diagnosed with DCIS (ductal carcinoma in situ), a common noninvasive cancer contained within the milk ducts that can become invasive over time if left untreated.
Treatment is normally a lumpectomy followed by radiation or a mastectomy – and remission rates are high.
Lee has chosen to undergo a double mastectomy because she did not want to be subjected to six to eight weeks of daily radiation and because, she says: "I never want to go through this again." After her mammogram, Lee had a biopsy to confirm the diagnosis, and underwent testing for BRCA1 and BRCA2, the genes that increase the risk of breast and ovarian cancer.
She tested negative, then consulted several doctors to help her make her choice of treatment.
"My doctor called me a poster girl for mammography," says Lee, who is glad she didn't wait until age 50 to get a mammogram, as new guidelines recommend.
When this is all over, the chef will have a new focus beyond food: "I plan to spread the word about early detection."
For more on Lee's cancer battle, pick up the latest issue of PEOPLE, on newsstands Friday