QUANTIFICATION OF PROSTATE-SPECIFIC ANTIGEN IMMUNOREACTIVITY IN HUMANBREAST CYST FLUIDS

The frequency of gross cystic breast disease in premenopausal women an d its possible association with increased breast cancer risk emphasise s the importance of investigations relating to breast cyst fluid compo sition. In order to contribute to a better analysis of this medium, we have measured the presence of prostate-specific antigen immuno-reacti vity in sixty-four human breast cyst fluids. Data analyses show that 3 5% of samples presented a level of this antigen < 0.05 mu g/L, whereas 42 out of 64 cysts show a significant increase in the mean value of m etabolically active apocrine cysts when compared to flattened cysts (p < 0.01). We report the first evidence that breast epithelium of gross cysts produces, secretes, and accumulates large amounts of prostate-s pecific antigen, a glycoprotein produced by prostatic tissue but recen tly detected in breast tumours, normal tissues, and during pregnancy. The production end intracystic accumulation of this serine protease in biosynthetically active apocrine type cyst can play a feasible role i n the natural history of gross cystic breast disease as well as in the mechanism of cyst formation, enlargement, and transformation.