- Breast density asymmetry is largely unrelated to established breast cancer (BC) risk factors.
- Localized asymmetry associated with a suspicious lesion could be a red flag.
Why this matters
- Mammographic breast density is a risk factor for BC.
- Prior findings have suggested that breast asymmetry may signal increased BC risk.
- The study included 854 women enrolled in the BREAST Stamp Project, all undergoing image-guided breast biopsy.
- Diagnoses were classified as nonproliferative benign breast disease (BBD; n=285), proliferative BBD (n=371), and in situ/invasive BC (n=198).
- Global bilateral asymmetry was defined as percent fibroglandular volume (%FGV) in the ipsilateral (biopsied) breast minus %FGV in the contralateral breast.
- Local bilateral asymmetry was defined as %FGV in a defined volume around the biopsy site minus %FGV in the corresponding site of the contralateral breast.
- No association was observed between global or local bilateral asymmetry and BC risk factors examined, including age, BMI, ancestry, and reproductive factors.
- A family history of BC was associated with global bilateral asymmetry in women with nonproliferative BBD:
- OR, 1.92 (95% CI, 1.14-2.23).
- No association was observed between global or local bilateral asymmetry and breast biopsy diagnosis.
- Compared to women with proliferative BBD, women with nonproliferative BBD were more likely to be in the fourth than in the first quartile of global absolute difference (greater asymmetry).
- Compared to women with proliferative BBD, women with in situ/invasive BC were more likely to be in the fourth than in the first quartile of local absolute difference.
- Ongoing work is focused on the relationship between bilateral breast density asymmetry and future BC risk.