• BRCA2
• new mutation
• hereditary breast cancer

Although it is widely stated that 5-10% of all breast cancers arise as the result of an inherited predisposition, the prevalence of mutations in BRCA1 or BRCA2 in unselected ascertainments of women with breast cancer is somewhat lower. In two population based series from the United States, presumably deleterious BRCA1 mutations were identified in only 14 female breast cancer patients out of a combined total of 884 women (1.6%).^1,2 In two European series, BRCA1 or BRCA2 mutations were identified in 19/1035 (1.6%) Finnish breast cancer patients³ and 24/1220 (2.0%) breast cancer patients from the UK.⁴ Because of the low prevalence of detectable mutations, screening of unselected breast cancer patients has not been recommended. Mutation analysis is more often suggested for specific groups of breast cancer patients in whom mutations are more likely to be detected. The decision whether or not to offer genetic testing usually revolves around the presence or absence of a significant family history of breast or ovarian cancer, although age at diagnosis, bilaterality, and ethnicity may be important considerations. A negative family history, however, clearly does not exclude the presence of a germline mutation in BRCA1 or BRCA2. In a population based series from the United Kingdom, none of the 13 mutation carriers diagnosed with breast cancer before the age of 36 was reported to have had a family history of breast or ovarian cancer in first degree relatives.⁵ In contrast, in a series from the United States, most mutation carriers in a group of women with early onset breast cancer had a history of breast cancer in either first or second degree relatives.⁶ However, even in this series, one of the mutation carriers had no family history of breast cancer. The lack of a family history among mutation carriers …