BRCA1 and breast cancer: Although a significant fraction of familial types of breast cancer could be explained by the inherited mutations of BRCA1, a large proportion of familial and sporadic types of breast cancer are not associated with mutations in BRCA1 (6–9) Furthermore, BRCA1 mRNA levels were also found to be reduced or absent in invasive sporadic types of breast cancer, thus assigning a role of BRCA1 in these as well (10–12).