Women who have benign breast disease are more likely to develop breast cancer, but the question that continues to baffle clinicians and researchers is which of these at-risk patients will actually develop a malignancy.

A recent analysis of more than 9,000 women over an average of 15 years suggests the answer lies in the details of their breast biopsies. More specifically, women with benign lesions whose biopsies revealed non-proliferative disease—fibrocystic changes consisting of only cysts, fibroadenoma, or columnar changes (Panel A)—had only a 27% greater risk of developing cancer, when compared to those with normal breasts (95% CI; 1.15–1.41). And those with either no family history of breast cancer or a weak one—the majority of women in this study—weren't at increased risk at all if they had non-proliferative lesions.

By way of contrast, women with atypical ductal or lobular hyperplasia (Panel B) upon biopsy faced more than a fourfold threat of cancer (95% CI; 3.26–5.41). Put another way, 64 of the 336 women in this study who had atypia developed a malignancy (19%).

Women with proliferative fibrocystic changes without atypia were at intermediate risk (Panel C) (RR 1.88, 95% CI; 1.66–2.12).

Hartmann LC, Sellers TA, Frost MH, et al. Benign breast disease and the risk of breast cancer. N Engl J Med. 2005;353:229-237.