Clinical implications of prostate-specific antigen in men and women.

Prostate-specific antigen (PSA) is a valuable tumor marker for prostate cancer. Although it is indeed produced at an extremely high level by the prostate, PSA is also expressed in many female tissues, especially those regulated by sex steroid hormones. PSA is detected in both normal and abnormal breast tissue, as well as in various breast fluids, including milk, nipple aspirate, and cyst fluid. Clinical studies suggest that the presence of PSA in breast tissue may indicate a favorable prognosis for breast cancer patients. Levels of PSA in nipple aspirate fluid, however, may be indicative of breast cancer risk. Concentrations of PSA in serum are elevated in pregnant women as well as in women who have excess androgens. More studies are necessary to determine the clinical implications of the presence of PSA in amniotic fluid and female serum.