Risk factors for ovarian cancer and early-onset breast cancer in Mongolia.

To determine if there are founder BRCA1 mutations in the Mongolian population.,Seventeen women with ovarian cancer, 14 women with premenopausal breast cancer and one woman with both cancer types were interviewed to obtain family history, and hormonal, reproductive and environment risk factor information. Blood was collected for DNA analysis from these women to determine the frequency of BRCA1 and BRCA2 mutations in Mongolia.,Two patients had two first-degree relatives with cancer and nine women had one first degree relative with cancer. Two women had the unique BRCA1 mutation previously described. These two women were not related but their parents were from the same tribe and they lived in the same imak (province). Only one other patient was of this tribal background and from the same region; however, she did not have the BRCA1 mutation.,A substantial proportion of Mongolian woman with ovarian cancer or early-onset breast cancer may be due to a founder BRCA1 mutation 3452delA.