Which family history characteristics increase the risk for breast cancer?

Updated: Dec 16, 2019
  • Author: Jessica Katz, MD, PhD, FACP; Chief Editor: Marie Catherine Lee, MD, FACS  more...
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Answer

Answer

A family history of breast cancer in a first-degree relative is the most widely recognized breast cancer risk factor, but only 5-10% of women diagnosed with breast cancer have a known genetic predisposition. Women with a family history of breast cancer in a mother or sister have a 1.5-3 fold increase in the risk of developing breast cancer. 

Family history of breast cancer is a heterogeneous risk factor that depends on the number of family members affected and the age at diagnosis, as well as the number of unaffected women in the pedigree. Even in the absence of a known genetic risk factor, the presence of a family history may suggest the presence of an unknown genetic risk, or a shared environmental risk.

A family history of ovarian cancer in a first-degree relative, especially if the disease occurred at an early age (< 50 y), has been associated with an increased risk of breast cancer risk. [12]   

The family history characteristics that suggest increased risk of cancer are summarized as follows [13] :

  • One or more relatives with breast or ovarian cancer
  • Breast cancer occurring in an affected relative younger than 50 years
  • Male relatives with breast cancer
  • BRCA1 and BRCA2 mutations
  • Ataxia-telangiectasia heterozygotes (4 times’ increased risk)
  • Ashkenazi Jewish descent (2 times’ greater risk; independent of BRCA positivity

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