Risk factors for benign breast disease and their relation with breast cancer risk. Pooled information from epidemiologic studies.

Information from published case-control studies on benign breast disease was pooled using standard statistical methods to obtain single, overall risk estimates. This analysis showed that higher socio-economic status (pooled relative risk, RR = 1.24, 95% confidence interval, CI = 1.13-1.37), later menopause (pooled RR = 1.87, 95%, CI = 1.67-2.11) and late age at first birth (pooled RR = 1.30, 95%, CI = 1.13-1.50) were associated with an increased risk of benign breast disease, whereas an apparent protection was given by greater body mass index (pooled RR = 0.58, 95%, CI = 0.50-0.67) and the use of oral contraceptives (pooled RR = 0.75, 95%, CI = 0.67-0.83). The role of these factors did not appear to be materially different in the various histopathologic categories considered, although available information allowed only a general distinction between breast dysplasia (fibrocystic disease) and benign tumors, chiefly fibroadenoma. In conclusion, the general evidence from published studies indicates that benign breast lumps appear to share a number of important risk factors with breast cancer.