Gross cystic disease (GCD) is a common benign breast condition. Previous studies have reported conflicting results regarding the relationship of GCD and subsequent risk of developing breast cancer. This cohort study was conducted to investigate the association of GCD and breast cancer among women at high risk for breast cancer.

The Women At Risk Registry provided the study population. The variables of interest included age at enrollment, age at breast cancer diagnosis, body mass index (BMI), presence of lobular carcinoma in situ (LCIS), and Gail scores. Statistical significance was determined by calculating multivariable-adjusted rate ratios using Cox proportional hazards regression model with years of follow-up as the time scale.

The study population included 1317 high-risk women, including 363 (28%) with GCD. The mean follow-up was 5.9 years for the GCD cohort, and 5.1 years for the non-GCD cohort (P < .001). The GCD and non-GCD groups differed by Gail score (P < .001), BMI (P < .01), presence of atypical hyperplasia (P < .001), presence of LCIS (P < .001), and family history of breast cancer (P < .001). Within the total population of 1317 women, 79 (6%) developed breast cancer; 28 (35%) out of the 79 had a prior history of GCD. Results from the Cox proportional hazards regression model showed a nonstatistically significant association of GCD and breast cancer (hazard ratio = 1.48, 95% confidence interval 0.88–2.51). The Kaplan-Meier overall survival estimate between the exposed and unexposed groups indicate that there are no differences in overall survival between the 2 groups (P = .5).

These results do not support the contention that gross cystic disease is a significant risk factor for breast cancer.