Benign lesions and cancer of the breast.

The retroprospective study of breast cancer in relation to benign breast lesions (BBL) involved an analysis of the breast cancer incidence in a cohort of women with a history of BBL. This cohort was formed on the basis of histological and cytological investigations performed during 1982-1991. A total of 10,776 cases with BBI were recorded, followed-up and analyzed. The total person-years of follow-up was 60,872. A total of 35 women with breast cancer were detected during the study. Cohort members with a BBL history were stratified into six subcohorts with respect to morphological and cytological patterns. Comparison of the observed breast cancer incidence with the expected breast cancer incidence calculated on the basis of the age-adjusted breast cancer incidence in the general population showed no significant rise in breast cancer incidence in the whole BBL cohort. The ratio of observed to expected incidence rates was 1.16. The analysis of subcohorts with diverse BBL patterns demonstrated a marked increase in breast cancer incidence only in the intraductal papilloma and cyst subcohorts. The ratios of observed and expected rates were 5.4 and 1.6, respectively. There was no significant difference from population levies of breast cancer risk in subcohorts with history of fibroadenoma, fibrocystic disease, breast nipple discharge and other lesions. Similar results were obtained in the prospective part of the study.