False positive prostate specific antigen values in the sera of women with renal cell carcinoma

The assessment of serum prostate specific antigen (PSA) with a polyclonal radioimmunoassay in 22 women with renal cell carcinoma resulted in measurable values in 6 patients, with the values ranging from 0.5 to 27.0 ng./ml. Tumor stage was T3 in all of these patients and the morphological features showed an eosinophilic subtype according to the German nomenclature. Additional measurements with a monoclonal radioimmunoassay in 3 of these 6 patients were negative as were all subsequent measurements postoperatively, although performed with the polyclonal radioimmunoassay. Immunohistochemical staining was negative for PSA. However, positivity for alpha-1-antichymotrypsin was detected, which was reported to occur in complexes with PSA and other proteases. Cross reaction between the polyclonal antibodies of the radioimmunoassay and 1 of these complexes is concluded. As far as clinical considerations are concerned, such cross reaction must be considered just as likely in male patients. Thus, it is recommended that therapeutic considerations in patients who underwent radical prostatectomy, for example, should not be exclusively based on PSA measurement performed with a polyclonal assay.