(Ivanhoe Newswire) -- Researchers know the BRCA gene mutation runs in families and increases a woman's risk of ovarian and breast cancer. Now, a new study shows a woman's risk of the disease due to the mutation may be underestimated in cases where two circumstances are true.

The first circumstance is being a victim of early onset breast cancer – which is linked to the genetic form of the disease. The second circumstance is having a "limited family structure" with no ovarian or breast cancer history. That refers to a woman having a family with less than two females who lived to age 45 or older in each lineage and didn't have breast or ovarian cancer. Having family members with the cancers is a major factor in current prediction models. But women with small families without a disease history could still be at risk for the genetic form – it might just not run in their family because there aren't many family members to potentially get it.

In this new study, out of the City of Hope in Durante, Calif., family structure was limited in 153 studied cases – 50 percent. BRCA gene mutations were detected in 13.7 percent of participants with limited family structure compared to 5.2 percent in "adequate" family structure. The researchers were quoted as saying, "… The databases of currently available probability models should be reanalyzed and limited family history recoded as a separate variable."

Today, genetic testing is available for women at risk for the BRCA mutation. Many women who test positive for it choose to have their ovaries removed and undergo mastectomies as preventive measures. As Sofia Merajver, M.D., (who was not involved in this new study) explained to Ivanhoe, "It might not be possible to prevent every cancer, but I think we will get to the point … that we will be able to control every cancer."

If a woman has a first-degree relative with the BRCA mutation she has a 50 percent chance of also having it. Having the mutation puts a woman at a 50 to 85 percent risk of breast cancer and a 16 to 50 percent risk of ovarian cancer.