Angelina Jolie, 37, wrote in The New York Times that she decided to have the operation after learning that she had a "faulty" gene, BRCA1, which "sharply increases my risk of developing breast cancer and ovarian cancer”.
"My chances of developing breast cancer have dropped from 87% to under 5%," Jolie wrote. "I can tell my children that they don't need to fear they will lose me to breast cancer."
In February Sharon Osborne reported that she too had a double mastectomy after testing positive for the breast cancer gene. In 2008 actress Christina Applegate also had a double mastectomy after she was diagnosed with breast cancer.
What is a mastectomy?
A mastectomy is the surgical removal of the breast, or in Angelina’s case, both breasts, usually as a treatment for breast cancer. There are three types of mastectomy, but the third type is now rarely carried out:
Local mastectomy: removal of the breast tissue and the fascia overlying the muscle underneath.
Modified radical mastectomy: removal of the breast tissue, the fascia and the lymph nodes under the arm.
Radical mastectomy: rarely done. Removal of the breast tissue, the lymph nodes and the underlying muscle and fascia.
How is a mastectomy carried out?
The type of incision into the skin depends on the size of the tumour, the type of tumour and whether or not breast reconstruction is going to be carried out immediately.
The breast tissue is pealed from the skin. As much possible of the skin and underlying fat are preserved in cases where a reconstruction is planned. In most cases the nipple and areola are removed along with the breast tissue.
Nipple-sparing surgery is only done in exceptional cases. The breast is then removed whole, with the covering of the muscle underneath. If a modified radical mastectomy is done then the lymph nodes are removed through the same incision.
Jolie said she completed three months of procedures at the end of April, and decided to go public "because I hope that other women can benefit from my experience. I wanted to write this to tell other women that the decision to have a mastectomy was not easy. But it is one I am very happy that I made," she wrote.
"I feel empowered that I made a strong choice that in no way diminishes my femininity."
Q & A on Angelina's surgery (via Associated Press)
Q: What kind of surgery did Jolie have?
A: Jolie had a preventative double mastectomy, meaning she chose to have both her breasts removed even though she had not been diagnosed with cancer.
Q: Why did she have the mastectomies?
A: Jolie says that she has a "faulty" version of the BRCA1 gene that means she has an 87 percent chance of getting breast cancer. By having both breasts removed preventatively, she said her breast cancer risk drops to 5 percent.
Q: How many women have this faulty gene?
A: Only a small percentage of women have this same faulty gene, or a similar mutated version of a related gene, BRCA 2. These mutations are most commonly found in women of Eastern European Jewish descent; one study found 2.3 percent of women in that group had the mutations — about five times higher than in the general population. Other ethnic groups, including the Norwegian, Dutch and Icelandic people, also have slightly higher rates of these mutations.
Q: How do these genes increase a woman's risk of breast cancer?
A: The average woman has a 12 percent risk of developing breast cancer sometime during her life. In comparison, women who have inherited a faulty version of a breast cancer gene are about five times more likely to get breast cancer. In the U.S., about 5 to 10 percent of breast cancers are thought to be linked to harmful versions of the BRCA1 and BRCA2 genes.
Q: How can women find out if they have these gene mutations?
A: A genetic test using a blood test can usually detect these genes. In the U.S., there are no standard guidelines recommending women for BRCA1 or BRCA2 genetic testing. The tests usually cost at least several hundred dollars.