Prevalence and differentiation of hereditary breast and ovarian cancer in Japan.

1534 Background: Breast cancer is the most common female cancer, according to the Center for Cancer Control and Information Service in Japan. However, the lifetime breast cancer risk in Japan is markedly lower (one in 16) than in the U.S. or Europe. We assembled needed data on the prevalence and characteristics of BRCA1/2 in Japan. Methods: Our study of BRCA 1 and 2 (BRCA1/2) collected data at 8 institutions in Japan on 320 individuals with a strong family history of breast cancer, according to the NCCN guidelines, by the end of March, 2012. Results: Among 260 proband cases, 46 (17.7%) were positive for BRCA1 and 35 (13.5%) were BRCA2 positive. Therefore, the total pathological mutation rate was 30.7%. Pathology data after breast surgery were obtained from 35 cases of BRCA1 mutation, 22 (62.9%) of which were triple negative and 10 (29.4%) were Luminal type. On the other hand, 24 cases (85.7%) of BRCA2 mutations were Luminal type. The most prevalent BRCA1 mutation site was L63X, found in 10 families. L63X ...