UPDATE AS OF DEC. 14: E! News reports that Giuliana Rancic is doing well after her double mastectomy, and that the surgery was successful. She also underwent reconstructive surgery after the mastectomy.
"G is doing really well," Rancic's husband, Bill, told E! News. "Her surgery lasted about four hours and the doctors were very pleased with the result."
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UPDATE AS OF DEC. 6: E! has released a statement to The Hollywood Reporter regarding Giuliana Rancic's decision to undergo a double mastectomy, saying that "we admire her courage and are proud to stand by her side through every step on her path to full recovery."
The Hollywood Reporter also said that the E! News host's last day on air before her double mastectomy will be Dec. 12, and that she will take two weeks off after undergoing the surgery to allow time for healing.
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Giuliana Rancic, who was diagnosed with breast cancer in October, announced on NBC's TODAY show that she will undergo a double mastectomy after learning that previous treatments did not work to completely rid her body of cancer.
Rancic told TODAY anchor Ann Curry that her desire to have children was a big part of her decision to have a double mastectomy. She had previously undergone a double lumpectomy (where just the tumor is surgically taken out of the breast, so that the entire breast does not have to be removed) but it was not completely successful.
"If I had chosen to just do another lumpectomy and then do radiation and then do anti-estrogen therapy, which means two to five years of medication, that basically puts me into early menopause, then I would have to put off having a baby for several years," Rancic said on TODAY. "So that was something we took into account. But to be honest, at the end it all came down to was just choosing to live and not looking over my shoulder for the rest of my life."
NBC Washington reported that if she had just had another lumpectomy, with radiation and anti-estrogen therapy, the chance of cancer returning could be as high as 40 percent, while a mastectomy would reduce the chance to less than 1 percent.
Christina Applegate, star of NBC's "Up All Night," also underwent a double mastectomy in 2008 in order to prevent the return of breast cancer. Actress Wanda Sykes also underwent a double mastectomy earlier this year because of breast cancer.
Mastectomy, or surgical removal of the breast or breasts, can be done both preventively -- for women who know they have a high risk of breast cancer, and don't want to take any chances -- or, in Rancic's case, as a treatment for breast cancer.
During a mastectomy, doctors remove all breast tissue from the breast. A doctor may recommend mastectomy over lumpectomy and radiation if a person has breast cancer has returned after previous radiation treatments, if you're pregnant and you can't undergo radiation, if you have a high genetic risk for returning breast cancer, if you have more than one tumor in different areas in the breast, or if you have an extremely large tumor that doesn't leave behind much healthy tissue, among other reasons, according to the Mayo Clinic.
Preventive mastectomy, also known as prophylactic or risk-reducing mastectomy, can decrease the risk of developing breast cancer by up to 90 percent, according to the National Cancer Institute.
There are a few different types of mastectomy; one type, called modified radical mastectomy, involves removal of the entire breast, meaning the tissue, areola, skin and nipple are removed, as well as part of the chest wall. Less radical mastectomies include simple mastectomy, where part of the chest wall is not removed; skin-sparing mastectomy, where the breast skin is not removed; and nipple-sparing mastectomy, where only the breast tissue is removed, according to the Mayo Clinic.
After a mastectomy, some women choose to undergo plastic surgery to reconstruct their breasts using breast implants and/or the women's own tissue, the Mayo Clinic reported. Women should talk to their doctors to find out if and what kind of reconstruction is right for them, the National Cancer Institute said.
The Daily Beast reported back in 2008 that only around 40 percent of people who undergo a mastectomy have their breasts reconstructed, though the National Center for Health Statistics does not track the actual rates of breast reconstruction.
Check out these other inspiring people, along with Rancic, who have received a breast cancer diagnosis in the past: