Growth inhibitory substances in human breast cyst fluid.

Women who have breast cysts with intracystic Na/K < 3 may have a higher risk of breast cancer than those with intracystic Na/K > 3. Low/undetectable concentrations of TNF alpha and IL-4, both of which have been shown to inhibit growth of human breast cancer cell lines, were found in the majority of breast cyst fluid samples. Intracystic oestradiol concentrations were significantly higher in the low electrolyte ratio group than in the high electrolyte ratio group. Imbalance between growth stimulatory and growth inhibitory substances in cystic breast disease may be an explanation for the higher risk of breast cancer particularly in the low electrolyte ratio group.