Four-generation pedigree showing autosomal dominant inheritance of a breast cancer gene. Breast cancer occurs in females in four generations. Note that the male carrier in Generation II has two daughters and a granddaughter with breast cancer. In a single family, a specific mutation occurs. Not all mutations result in the occurrence of breast cancer.
Some mutations are in silent areas of the gene and are never expressed.
We know, for example, that estrogen, whether manufactured by your body or taken by prescription, is a primary risk factor. Remember that even a woman without that mutation still has a lifetime background risk for breast cancer of one in eight. There are already over 200 mutations identified on BRCA1 and BRCA2. BRCA2 genes may have to be examined to determine which one of the many mutations is present. Such testing is not typically covered by health insurance policies.