Table 5 Prevalence of deleterious mutations in BRCA1 and BRCA2 based on this study

From: Genetic and clinical characteristics in Japanese hereditary breast and ovarian cancer: first report after establishment of HBOC registration system in Japan

Family history of breast cancer or ovarian cancer Among first- and second-degree relatives No family history of breast or ovarian cancer Family history in only third-degree relatives
Breast cancer <50 y + +   
Ovarian cancer (at any age) + +   
Patient’s history
 Breast cancer ≥ 50 y 2/58 9/58 6/24 1/8 0/26 0/8
  3.4% 15.5% 25.0% 12.5% 0% 0%
 Breast cancer < 50 y 21/125 45/139 27/61 17/27 16/164 1/17
  16.8% 32.4% 44.3% 63.0% 9.8% 5.9%
 Ovarian cancer with no breast cancer at any age 0/2 1/1 1/2 1/5 0/1
  0% 100% 50.0% 20.0% 0%
 Breast cancer and ovarian cancer at any age 1/1 1/2 4/4 1/6
  100% 50% 100% 16.7%
 Male breast cancer at any age 0/1 0/1 0/1
  0% 0% 0%
 No breast cancer or ovarian cancer at any age 0/16 2/27 3/20 0/7 1/4 0/1
  0% 7.4% 15.0% 0% 25.0% 0%