Esterase, estradiol and sex hormone-binding globulin in breast cyst fluid.

Women who have palpable breast cysts lined by apocrine epithelium (intracystic Na/K < 3) may have a higher risk of developing breast cancer than those with breast cysts lined by flattened epithelium (intracystic Na/K > 3). Esterase converts fatty acid esters of E2 to unconjugated E2 and could conceivably modulate intracystic E2 concentrations. The amount of SHBG in BCF may regulate the amount of unbound, biologically active E2 present. In this study the relationships amongst E2, esterase, SHBG and Na/K in BCF were assessed. Negative correlations were found between E2 and esterase (P<0.05), E2 and SHBG (P<0.001), and E2 and Na/K (P<0.001). A positive correlation was found between SHBG and Na/K (P<0.001). No correlation was found between esterase and Na/K. The findings of this study suggest that esterase is unlikely to be important in modulating intracystic E2 concentrations.