Normal genetic testing results don't guarantee healthy genes. In some families, many women have had breast cancer, yet they all test normal for the known breast cancer mutations. These families may have an inherited form of breast cancer caused by a genetic abnormality that hasn't been identified yet.
Abnormal genes are just one of many risk factors for breast cancer. Most cases of breast cancer do not involve an altered BRCA1 or BRCA2 gene. Statistics show that at most, 1 in 10 breast cancers cases involve an inherited altered gene.
The bottom line is that the absence of altered BRCA1 or BRCA2 genes is by no means a guarantee against developing breast cancer.