Detection of nonprostatic PSA in serum and nonserum samples from women

Prostate-specific antigen (PSA) has been characterized as a specific prostate marker, although recent studies have suggested the existence of PSA of nonprostatic sources. We have assessed the presence of PSA by an ultrasensitive assay in 276 serum and nonserum samples from women. Our data show the presence of PSA in 90% of nonserum samples, including milk secretions, breast cysts, amniotic fluids and broncho-alveolar washings. We have also detected its presence in 58% of the sera tested, although it only exceeded 0.1 microg/l in 6 of the cases. We conclude that PSA can no longer be considered a specific prostate tissue marker; since the concentrations detected in women's serum are ultralow, this finding appears to interfere minimally with its value as a tumoral marker.