Background: The evidence on the relation of family history of cancers other than breast cancer to breast cancer risk is conflicting, and most studies have not assessed specific breast cancer subtypes.

Methods: We assessed the relation of first-degree family history of breast, prostate, lung, colorectal, ovarian, and cervical cancer and lymphoma or leukemia, to the risk of estrogen receptor–positive (ER+), ER−, and triple-negative breast cancer in data from the African American Breast Cancer Epidemiology and Risk Consortium. Multivariable logistic regression models were used to calculate ORs and 95% confidence intervals (CI).

Results: There were 3,023 ER+ and 1,497 ER− breast cancer cases (including 696 triple-negative cases) and 17,420 controls. First-degree family history of breast cancer was associated with increased risk of each subtype: OR = 1.76 (95% CI, 1.57–1.97) for ER+, 1.67 (1.42–1.95) for ER−, and 1.72 (1.38–2.13) for triple-negative breast cancer. Family history of cervical cancer was associated with increased risk of ER− (OR = 2.39; 95% CI, 1.36–4.20), but not ER+ cancer. Family history of both breast and prostate cancer was associated with increased risk of ER+ (3.40; 2.42–4.79) and ER− (2.09; 1.21–3.63) cancer, but family history of both breast and lung cancer was associated only with ER− cancer (2.11; 1.29–3.46).

Conclusions: A family history of cancers other than breast may influence the risk of breast cancer, and associations may differ by subtype.

Impact: Greater surveillance and counseling for additional screening may be warranted for women with a family history of cancer.