Most breast and ovarian cancers occur by chance and are classified as sporadic cancers. However a number of breast and ovarian cancers, are due to an inherited predisposition. This means there is a higher chance a person will develop certain types of cancers in their lifetime compared to someone in the general population. These hereditary cancers are due to an underlying genetic cause. For some families this underlying genetic cause is found (this is called a gene fault/mutation), but for most families the underlying genetic cause is not found.