Family History and Age as Risk Factors for Breast Cancer

By Priyanka Varma, Barbara Guido

BURLINGAME, Calif. Nov 23rd, 2021

Family History and Age are two factors, amongst others, contributing to having a high risk of developing Breast Cancer. Up to 30% of those diagnosed with breast cancer have a positive family history [1]. The National Comprehensive Cancer Network guidelines describe the familial risk of getting Breast Cancer into three categories, Average, Moderate, and Strong [2,3]. 

An “average” risk is defined as a risk similar to that in the general population. Patients with no first (parents, brothers, sisters, children) or second (aunts, uncles, nieces, nephews, grandparents, grandchildren) degree relatives with Breast cancer or one second degree female relative with breast cancer (in one breast only) diagnosed after the age of 50 years are classified under “average” risk [3]. 

A “moderate” risk on the other hand is higher than the general population but most patients under this risk will not develop breast cancer. This will encompass patients with one or two first degree relatives, or two second degree relatives with breast cancer (in one breast only), with both relatives diagnosed after age 50, or one or two first or second degree relatives with high grade prostate cancer [3]. 

A “strong” risk has a risk higher than the general population, but not all women in these families will develop breast cancer. This will have patients with one (or more) first or second degree relative(s) with breast cancer diagnosed at age 45 or younger in women or triple negative breast cancer diagnosed at age 60 or younger in women, or primary cancer of both breasts, or both breast and ovarian cancer in the same relative, or male breast cancer, or ovarian cancer, or two or more first or second degree relatives from same side of the family with breast cancer, if at least one breast cancer was diagnosed before age 50, or three or more first or second degree relatives from the same side of the family with breast or high grade prostate cancer at any age [3].

The risk of breast cancer is about two times higher for women with one first-degree relative with breast cancer, compared to women without a family history [4]. A moderate family history risk for most women will be considered a strong risk for women of Ashkenazi or Jewish ancestry and they should be screened for BRCA1 and BRCA2 mutations [3].

The incidence of breast cancer increases with age. 82% of invasive breast cancer is diagnosed in women aged 50 and older [5]. The risk of breast cancer is highest for women in their 60s with invasive breast cancers diagnosed in 1 in 28 women in their 60s [6].


  1. Lilyquist J, Ruddy KJ, Vachon CM, Couch FJ. Common Genetic Variation and Breast Cancer Risk-Past, Present, and Future. Cancer Epidemiol Biomarkers Prev. 2018 Apr;27(4):380-394. doi: 10.1158/1055-9965.EPI-17-1144. Epub 2018 Jan 30. PMID: 29382703; PMCID: PMC5884707.
  2. genetics_bop.pdf (
  3. Breast and Ovarian Cancer and Family History Risk Categories | CDC
  4. Breast Cancer Risk Factors: Family History
  5. Breast cancer statistics, 2019 - DeSantis - 2019 - CA: A Cancer Journal for Clinicians - Wiley Online Library
  6. Breast Cancer Risk in American Women - National Cancer Institute

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