Preventive mastectomy is an operation some women consider if they or their doctors feel they are at an increased risk of developing breast cancer.
The former X-Factor judge Sharon Osbourne had a double mastectomy after being told she carried genes which increased her breast cancer risk.
Around 48,000 women get breast cancer in Britain each year. Breast cancer also affects men, but in lower numbers.
Genetic testing is offered to women with a higher risk of breast cancer, such as having close family relatives with cancer. The test screens for faulty genes called BRCA1 and BRCA2.
A woman will usually be referred for genetic screening via her GP because of concerns about a family history of breast cancer.
The screening clinic will work out how high the risk is that they might carry a genetic fault.
There will be an explanation the genetic testing process, what the results could be, what the different results could mean for the woman.
The genetic test results will be known in two to eight weeks. These will be discussed with a counsellor to talk about available options.
The first stage of genetic testing looks at DNA of a relative who has breast cancer or had breast cancer to look for genetic faults.
A negative test result means the genetic mutation wasn't found. This result is inconclusive, ruling out some possible explanations for breast cancer in the family.
If the relative's test is positive, predictive or mutation testing is offered.
A negative test result means the gene fault has not been inherited and in turn, cannot be passed on to your children.
A positive test means the fault is present, and the next steps and options will be discussed.
Special tests are available for people of Ashkenazi Jewish descent, as additional genetic faults are sometime found in this group.
Is preventive mastectomy effective?
Does preventive mastectomy mean no further risk of breast cancer? The charity Breast cancer Care says you can never completely remove the risk of breast cancer, but the operation does drastically reduce the risk.
Making the decision to have breasts removed is far from easy to make, and the NHS will make a special counsellor available to help.
The operation is called bilateral prophylactic mastectomy and aims to remove all breast tissue that potentially could develop breast cancer. Preventive breast cancer surgery also may be considered if a woman has already had breast cancer and is therefore at increased risk of developing the disease again in either breast.
Another procedure which may be considered is an oophorectomy. This is the surgical removal of the ovaries and Fallopian tubes. This procedure has been found to reduce the risk of breast cancer with a family history of the condition and who have not yet been through menopause. The risk of ovarian cancer is also reduced.
After the breasts have been removed, breast reconstruction may be carried out at the same time as the mastectomy or at a later date.