The Genetics of Breast and Ovarian Cancer

According to the National Cancer Institute (NCI), the lifetime risk for a woman to develop breast cancer is 12.8 percent or one in eight, while the lifetime risk to develop ovarian cancer is a little greater than 1 percent (1.4 percent, or one in 70).

Approximately 5 percent to 10 percent of breast and ovarian cancers are due to known predisposing genetic factors. This means that the majority of breast and ovarian cancers are, in fact, not inherited. Consider the following:

• Of those cases of breast cancer that are inherited:
  
  
  • 20 percent to 40 percent are due to mutations in the BRCA1 gene
    
    
  • 10 percent to 30 percent are due to mutations in the BRCA2 gene
    
    
  • <1 percent are due to mutations in the P53 gene
    
    
  • <1 percent are due to mutations in the PTEN gene
    
    
  • 30 percent to 70 percent are due to other genes
    
    
• Of those cases of ovarian cancer that are inherited:
  
  
  • 70 percent are due to mutations in the BRCA1 gene
    
    
  • 20 percent are due to mutations in the BRCA2 gene
    
    
  • 2 percent are due to mutations in the genes that cause HNPCC (hereditary nonpolyposis colorectal cancer)
    
    
  • 8 percent are due to other genes

There are several genetic syndromes associated with an increased risk for breast and/or ovarian cancer that require clinical care by a physician or other healthcare professional. Listed in the directory below are some, for which we have provided a brief overview.

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