Immunohistochemical localization of prostate-specific acid phosphatase and prostate-specific antigen in stage A₂ adenocarcinoma of the prostate: Prognostic implications

Previous immunohistochemical studies with prostate-specific acid phosphatase and prostate-specific antigen documented the diagnostic value of these antigens in the identification of metastatic prostatic adenocarcinomas and in the differentiation of primary prostatic adenocarcinomas from poorly differentiated transitional cell carcinomas. Although attempts have been made to correlate immunostaining with degree of tumor differentiation, no study has directly assessed the relation of either prostate-specific acid phosphatase or prostate-specific antigen immunoreactivity of tumors with their biologic behavior. Nineteen patients with predominantly intermediate Gleason grade untreated stage A₂ carcinomas of the prostate were studied by the unlabeled antibody immunoperoxidase technique for prostate-specific acid phosphatase and prostate-specific antigen in an attempt to identify those in whom the disease would progress without further therapeutic intervention. Of the 12 carcinomas with areas of either weak or negative prostate-specific acid phosphatase staining, nine progressed. Two of the seven carcinomas that did not have these foci of poor immunostaining also progressed. Although there was a trend for foci of poor immunoreactivity to predict tumor progression, the correlation was not significant. All seven patients who had tumor foci with weak or negative prostate-specific antigen immunostaining experienced progression of the disease. Of the 12 patients with only moderate or intense staining, the tumors did not progress in eight. This correlation between foci of poor immunoreactivity and progression of disease was statistically significant. When the study was repeated by varying the technique without awareness of previous grading results, the same predictive results were obtained. When results of prostate-specific antigen immunostaining were compared with those achieved with prostate-specific acid phosphatase, the superiority of the prostate-specific antigen antisera for Iabeling prostatic tissue was evident. This study suggests that prostatic cancers consist of subpopulations of cells with differing immunoreactive properties and that the presence of cells that lack sufficient differentiation to express normally present immunologically recognizable antigens is an indication of potentially more aggressive neoplasms.