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Though her mom had battled breast cancer, Sarah Lien, 24, certainly wasn’t ready to start worrying about herself. After all, she was young, and her mom, Barbara Hawkins, had tested negative for the BRCA1 and BRCA2 mutations, the genetic markers most commonly linked with a high risk of breast cancer.

But one day, as Lien was showering, she felt a walnut sized lump in her breast.

“I crumpled on the bathroom floor and I just started bawling” Lien told NBC News chief medical editor Dr. Nancy Snyderman. "And so, of course, it was late at night and the first person I call is my mom.”

Hawkins was just finishing up her own breast cancer treatment and was stunned by the revelation.

“I could not even believe it,” Hawkins said.

Even more shocking was the news delivered by Lien’s doctors: She had Stage 3 breast cancer.

Lien scrutinized her family tree and noticed that there was a lot of breast cancer in the women on her father’s side. Even more surprising, her father’s father was a breast cancer survivor. Once her grandfather learned of Lien’s diagnosis, he got tested and sure enough, he carried the BRCA gene mutation.

People often forget about the father’s side of the genetic equation, said Dr. Susan Domchek, executive director of the Basser Research Center for BRCA at the University of Pennsylvania, the only center in the nation devoted to research on prevention and treatment of cancers related to BRCA mutations.

That’s partly explained by the fact that men, even with the gene, are much less likely to develop breast cancer, Domchek told NBCNews.com.

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“Men with these mutations have a 5 to 10 percent risk of developing breast cancer,” she said. “In the general population, the risk of breast cancer in men is 0.1 percent.

If there is breast cancer in a male relative, “that should be a big red flag,” Domchek said.

BRCA mutations have been in the news a lot lately, with celebrities like Angelina Jolie opting to have both breasts removed after learning she had a BRCA mutation even though she had not developed cancer.

With all the news coverage, the mutations “seem like a virtual epidemic right now,” Domchek said. “But it’s actually one in 500 to one in 800 that have the mutations. It is much more common in certain groups, however, like people of Ashkenazi Jewish descent: For them, it is 1 in 40. And in those under 40 with breast cancer, it’s 1 in 10.

“But even among those groups, a diagnosis before age 25 is very uncommon.”

Once Lien learned that her grandfather tested positive, she realized she’d need to get tested herself to make the best treatment choice. When her results came back positive for BRCA2, the young newlywed who had made plans to see the world before settling down and have children realized she was going to have to make some tough choices.

Lien opted to take an aggressive approach — a double mastectomy along with chemotherapy and radiation.

It’s a strategy that more and more BRCA positive women are choosing to reduce the risk of recurrence, experts say.

Lien’s doctor explains the choice this way. “It’s really driven by the patient who wants some peace of mind,” said Dr. Kristine Calhoun, an associate professor in the department of surgery at the University of Washington. “They want to take control of some of the situation.”

Bilateral mastectomy is very common among women who learn they are positive for one of the BRCA mutations at the time of their breast cancer diagnosis, Domchek said. That’s because the risk of a recurrence is very high for this group of women.

For Lien, the results of the genetic test not only guided her treatment, they also pushed her and her husband to plan ahead for the children they had always known they wanted.

“I was diagnosed one day,” Lien said. “We were in the fertility clinic the very next day.”

The couple froze embryos before Lien started her chemotherapy.

And now, cancer free, Lien is just weeks away from having a baby that grew from one of those frozen embryos.

“When I found I was expecting, I was thrilled,” Lien said. “My heart was so joyful.”

“I had this perfect fairy tale planned out for my life and it did take a little bit of a detour,” she added, “but we’re right back on the road we want to be on.”