BRCA1 and breast cancer: The twenty founder mutations were detected in 421 of 1018 (41%) Polish women with a strong family history of breast cancer (the mean number of breast cancers per family was 3.6 and the mean age of diagnosis of the probands was 44 years), including BRCA1/2 alleles seen in 354 cases and non-BRCA1/2 mutations seen in 67 cases [4].