Evaluation of human breast cysts according to their biochemical and hormonal composition, and cytologic examination.

Breast cyst fluids were aspirated during the mild luteal phase of the menstrual cycle from 88 patients with gross cystic disease. According to intracystic Na+/K+ ratio three categories of cyst were identified: Type I with low Na+/K+ ratio, low levels of chloride, glucose, and pH, and high concentrations of dehydroepiandrosterone-sulphate (DHAS) and apocrine epithelium; Type II with high Na+/K+ ratio presenting levels of chloride, glucose, pH, and DHAS similar to those found in plasma, and flattened epithelium; Type III with intermediate values for the above parameters. The findings suggest that the cysts could correspond to the different functional stages of the epithelium lining the cysts. Cyst classification was evaluated using a discriminant analysis, which allows breast cyst fluids to be assigned within a category defined by the Na+/K+ ratio. The apparent correct rate for each category was more than 87%. The variables that better discriminate among groups of cysts were chloride, glucose, intracystic prolactin, and pH, respectively. These discriminant functions could be used as criteria for an optimal classification of breast cysts, which might help study of the epidemiology of breast cancer and its relationship to gross cystic disease.