( CNN ) -- I first saw the headline early Tuesday on Real Clear Politics , a political news site where I generally start my morning . It 's not where I expect to see a story on breast cancer . Then I checked my e-mail messages -- they all seemed to be about Angelina Jolie 's op-ed . Students in my undergraduate class wanted to discuss it in our next session . Colleagues expressed concern and wondered what the right response was . People I do n't even know sent e-mails . One , from a research fellow at the International Agency for Research on Cancer , nicely summed up the general concern : `` I fear that this disclosure will motivate other women to undergo preventive mastectomy , even though they do not need it . '' Wow . Maybe I should read it . I did . I found it to be a moving story and understood her choice . What I could n't understand initially was the concern expressed by others . As the day wore on , the story dominated the news . I did n't fully appreciate how much Ms. Jolie is admired and respected and had neglected to consider just how powerful a celebrity personal anecdote could be . If American women saw themselves in Angelina Jolie -- then that would be a problem . Because the logical next question is : Should I get a preventive mastectomy ? Then I realized something was missing in her piece ; something that should have been printed in big black letters : . NOTE : This story is not relevant to more than 99 % of American women . Why ? Because more than 99 % of women do not have the BRCA1 mutation -- or the BRCA2 mutation , for that matter . Let 's be clear , the BRCA1 mutation is a bad thing . Although I might quibble with the exact numbers in the piece , the big picture is this : the mutation increases the risk of developing breast cancer about five fold and increases the risk of ovarian cancer more than 10 fold . It is a powerful risk factor for these cancers -- almost as powerful as cigarette smoking is for lung cancer . When people are at very high risk for something bad to happen , preventive interventions are more likely to be a good deal ; that is , the benefits are likely to exceed the harms . I 'm not saying that prophylactic mastectomy is the right choice for a woman with BRCA1 , simply that it is a reasonable one . When people are at average risk , the deal changes . The opportunity for benefit is less , simply because the bad event is less likely to happen . But the harms of preventive intervention remain roughly the same . It is a fundamental precept of medicine -- one I hammer home with undergraduates ( future patients ) and medical students ( future doctors ) : Patients with severe abnormalities stand to gain more from intervention than patients with mild ones . Patients with mild abnormalities are more likely to experience net harm from intervention , simply because they have less opportunity to benefit . The vast majority of women do n't have the BRCA1 mutation . They are at average risk for breast cancer . They are not Angelina Jolie . They should not have a preventive mastectomy . A few weeks ago , in a New York Times Magazine piece , Peggy Orenstein related her first instinct when facing breast cancer recurrence : take the other breast too . Her oncologist responded with a simple question : `` Would an average woman cut off her breasts ? '' I hope not . But there is a second question for women raised by Ms. Jolie 's piece : Should I be tested for BRCA1 ? She seems to believe the answer is yes , pointing to the half-million women who die from breast cancer worldwide each year . But she neglects to point out that 90 % of these deaths have nothing to do with the BRCA1 mutation . That 's because most women do n't have the mutation and because most breast cancer is sporadic . Opinion : Jolie 's choice : Risks and benefits . The few women who are likely to have the mutation are also likely to know they may have it based on the oldest genetic test of all : a strong family history of cancer . Population-wide screening raises complex issues . We would want to know more about how often the test is wrong , particularly how often the test is falsely positive . That 's important because women falsely diagnosed as a mutation carrier might undergo prophylactic mastectomy unnecessarily . Then there are the psychological effects , not only for the patient but also for her siblings and offspring . We 'd also need to know more about what a BRCA1 mutation means in the absence of family history . Ms. Jolie 's mother died of ovarian cancer at age 56 . I 'm no geneticist , but I can guess that puts her at higher risk -- both for having the mutation and for developing a bad cancer . And we 'd certainly want an answer to the question : Must the test cost so much ? There 's no one right choice for a woman in Angelina Jolie 's position , but she may well have made the right choice for her . Luckily it is a choice most women do n't have to face . The opinions expressed in this commentary are solely those of H. Gilbert Welch .
Professor of medicine Gil Welch surprised by huge response to Angelina Jolie 's op - ed . Welch thinks women might wonder if they , too , should have preventive mastectomies . Welch : But 99 % of women do not have the BRCA1 mutation that raises the risk of breast cancer . He believes women should look at family history before getting tested for the mutation .