Shifted distribution of cation-related cyst types in post-menopausal patients with gross cystic disease of the breast.

Gross cystic disease of the breast (GCD) is rarely seen after the menopause. Recent work has shown that by measuring electrolytes in the breast cyst fluid (BCF) it is possible to identify two principal classes of cyst, designated Type 1 (K+/Na+ greater than 1.5) and Type 2 (K+/Na+ less than 0.66). A smaller, intermediate class (Type 3) also appears to exist. We measured K+, Na+ and dehydroepiandrosterone sulphate (DHA-S) in 38 BCF samples aspirated from 33 women with GCD who had undergone spontaneous menopause at least 1 yr previously. Statistically significant correlations were found between DHA-S and cations (positive in relation to K+, P less than 0.001; negative in relation to Na+, P less than 0.001). The distribution of cyst types was shifted with respect to that characteristic of cases that occur at an earlier age: whereas Type 1 cysts predominate in menstruating women, Type 2 cysts proved more numerous in the post-menopausal subjects. The difference was statistically validated (P less than 0.001). The results seem to indicate a sharp reduction in high K+, high DHA-S cysts after the menopause, which may be paralleled by a decrease in the associated apocrine metaplasia. In view of the major biochemical differences between Type 1 and Type 2 cysts and of the suggested differences as regards cancer risk, classification of post-menopausal patients with GCD by cyst type is critical prior to any clinical trial or follow-up.