The gross cystic disease (breast cyst < 3 mm in diameter) is common benign disease of the breast. The relations GCD with breast cancer remain the fundamental problem. Although the cysts itself only exceptionaly degenerates into cancer, the presents of macrocystic disease multiplies by 3 to 4 the risk of cancer. A lot of interesting examinations were performed on cyst fluids aspirated from patients to identify women with benign breast disease and particular risk for breast cancer. There are two groups of breast cysts: these lined by apocrine epithelium and those lined by flattened epithelium. It is generally accepted that measurement of intracystic [Na+]/[K+] is a simple way of differentiating between these two groups of cysts. Higher intracystic concentrations of same substances may provide an explanation for the higher risk of breast cancer, which has been observed in low electrolyte group. Breast cyst fluid samples were analyzed for a lot of hormones, proteins, specific growth factors, adhesion molecules, bile acids, tumor markers and their levels were compared with breast cancer risk. At the present time, the biochemical measurements in cyst fluids aren't popular to identify women likely to develop breast cancer. We should use other diagnostic methods to examine these patients.