The epidemiology of gross cystic disease of the breast confirmed by biopsy or by aspiration of cyst fluid.

: This study concerns 3443 patients treated by 1 physician for benign breast conditions, with follow-up on 94% of the patients averaging 19 years. Over three quarters of these patients had gross cystic disease (GCD) of the breast confirmed by aspiration of cyst fluid or by biopsy. Diagnosis of GCD by microscopic pathology review alone is shown to have high error rates when compared with information in the operative report and the gross pathology report. The risk of subsequent breast cancer for GCD patients was more than double the rates in the general population, and about the same as that of patients with no GCD who had biopsy findings of benign proliferative disease. Among patients with aspirations for GCD and no biopsy, there was a trend of increasing risk of subsequent breast cancer with increasing numbers of aspirations, with a sixfold relative risk for patients with ten or more aspirations.