Oral contraceptive use and fibrocystic breast disease of different histologic classifications.

The relationship between oral contraceptive (OC) use and occurrence of fibrocystic breast disease (FBD) of different histologic classifications was evaluated with data from a cohort study. Biopsy specimens from 232 women with FBD were classified into different atypia categories. In 96 matched pairs of OC users and nonusers, atypia scores were lower in users than in nonusers. Women without breast diseases (500 OC users and 500 nonusers) were sampled from the original cohort to form a two-stage "anamorphic" study with the 232 cases of FBD. The previously shown inverse association between OC use and FBD occurrence was present and increased with increased length of OC use. However, the "protective effect" of OC use did not vary for different histologic classifications of FBD. The findings from both paired and anamorphic analyses of the data are not consistent with the hypothesis that the use of OC is associated with decreased frequency only of FBD with minimal epithelial atypia.