While the media has focused a lot of attention on Angelina Jolie’s decision to have a preventive double mastectomy, her genetic cancer risk has received much less notice. In fact, many medical experts commenting on her announcement have gone out of their way to reassure women that her situation is relatively rare. But one in 10 is not rare at all.

The sweet woman sitting at the front desk of the breast cancer center also put it that way: “It’s only 10 percent” of breast cancer cases that are hereditary, she said. She was a staff member and I was volunteering to be one of the “buddies” who talk with women concerned about breast cancer. In particular, I had offered to talk with women concerned about genetic breast cancer, but the woman at the desk clearly wasn’t impressed with my offer. She paused for a moment, as if she were considering my suggestion, and then added, “I don’t think very many of our clients would need this. Only 10 percent of breast cancer is genetic.”

My doctors have told me this; even my genetic counselors have told me this. They all use the same phrase, “Only 10 percent,” as if the words were glued together, or as if this were a small number.

Because I hear this phrase so often,some part of me wanted to shout at this woman, “Only 10 percent! That’s a lot of women!” But she was warm and friendly and I knew she wanted to help women, too. I also knew that 10 percent of a really big number is still a big number.

And I want all of us to think about the meaning of what she told me:

Almost one in 10 of the women who get breast or ovarian cancer are born with a gene that could warn them. Advance warning could give them choices for early detection and even for prevention — but most of them still don’t know.

In the U.S. alone, close to 300,000 women are diagnosed with breast cancer every year. That means 300,000 this year, 300,000 next year, the year after that, and every year until we find a cure. Globally,1.6 million women are diagnosed every single year.

I often think about those 300,000 women who are newly diagnosed with breast cancer, and imagine how their stories will unfold. A woman will feel a lump in her breast and will be very worried. She’ll feel a bit of panic rising inside that she’ll try to ignore; she’ll hope the lump is just a cyst, that it is nothing. Or maybe she will have a mammogram and the technician will ask her to stay just a bit longer so the radiologist can take another look. Or she will get a phone call from her doctor about a “suspicious spot” on her test, that probably is nothing, but could she please come back in.

She may move on to an ultrasound or an MRI and eventually to a biopsy. Not long after, she will get the phone call she will always remember or will have her doctor ask her to come in to talk in person, and she will first hear the words, “You have breast cancer.” This is a terrible moment, a phone call full of pain or an unreal conversation in a doctor’s office. It may feel as if her life as she has known it has come to an end, suddenly, without her permission.

In the next year, almost 300,000 women in the United States will get this call.

Another 22,000 women each year will get the news that they have ovarian cancer—a diagnosis that is much more dangerous because by the time a woman feels symptoms, her cancer has most likely already spread. Without an early warning, a woman may feel fine until her cancer is no longer treatable. In the United States, more than 14,000 women each year die from ovarian cancer, known in treatment centers as “the silent killer.”

For nine out of 10 of these women, there currently is nothing we can do to help them in advance. Their diagnoses of breast or ovarian cancer are sporadic, random, impossible to predict. But 10 percent of these women can learn their risk ahead of time. They can take steps that make it extremely unlikely that they will ever get this call.

Genetic cancer is a family disease. Every woman who comes into this breast cancer center with genetic breast cancer very likely has a large network of family members who are also at risk. If she doesn’t yet know her risk, they probably don’t know theirs either. I imagine each woman in this 10 percent walking in surrounded by an invisible circle of family members whose futures are also at stake.

I think about these things because I am one of the one in 10. I learned my genetic risk for breast and ovarian cancer five years ago, and then scrambled to learn everything I could about my options for preventing these with hormone treatment or surgeries. After two very intense months of recalling my mom’s death from ovarian cancer and her father’s death from pancreatic cancer, I made the very difficult decision to have a preventive double mastectomy with reconstruction. I vowed to take any step I could to avoid cancer. Then, after a normal mammogram, I had an MRI that showed I already had breast cancer. It was too late for my surgery to be preventive.

I wanted the woman at the desk at the breast cancer center to notice these women with genetic cancer risk because they could have been me. I didn’t want her to dismiss them because they were “only” 10 percent.

So I took a deep breath and asked, “This ‘only 10 percent’ thing…can we talk about this?”

Lisa Friedman, Ph.D., is a partner in the Enterprise Development Group, an innovation consulting firm based in Palo Alto, Calif., and an adviser for Facing Our Risk of Cancer Empowered, (FORCE), a nonprofit offering information and support about hereditary breast and ovarian cancer (www.facingourrisk.org).