Cancer risk, even among those with similar environmental exposures is not uniformly distributed. Although we have been able to identify genetic factors whose variants appear to significantly alter an individual's risk of developing breast cancer (BRCA1 and BRCA2), these genes are likely involved with less than 10% of breast cancer cases. Perhaps more applicable to the general population are genes which, while not directly involved with the oncogenic process, may have variants (polymorphisms) which act indirectly by increasing the risk of an oncogenic change within a cell.