PROSTATE-SPECIFIC MEMBRANE ANTIGEN EXPRESSION IS GREATEST IN PROSTATEADENOCARCINOMA AND LYMPH-NODE METASTASES

Objectives. Prostate-specific membrane antigen (PSMA) is an integral m embrane protein highly specific for the prostate. PSMA may be clinical ly useful for predicting outcome in patients with prostate cancer. We compared the expression of PSMA in prostate adenocarcinoma and lymph n ode metastases in a large series of patients with node-positive cancer . Methods. We studied 232 patients with node-positive adenocarcinoma w ho underwent bilateral pelvic lymphadenectomy and radical retropubic p rostatectomy at the Mayo Clinic between 1987 and 1992. Immunohistochem istry was performed using monoclonal antibody 7E11-5.3 directed agains t PSMA. For each case, the percentage of immunoreactive cells in benig n prostate tissue, adenocarcinoma, and lymph node metastases was estim ated in 10% increments. Intensity was recorded using a scale of 0 to 3 (0 = no staining, 3 = highest). Results. Cytoplasmic immunoreactivity for PSMA was observed in all cases in benign epithelium and cancer, a nd most lymph node metastases. The number of cells stained was lowest in benign epithelium; cancer and lymph node metastases were similar (4 6.2% +/- 27.5% versus 79.3% +/- 18.5% Versus 76.4% +/- 26.1%, respecti vely; all pairs P < 0.05). Intensity of staining was greatest in prima ry cancer and lowest in lymph node metastases. Conclusions. PSMA is ex pressed in benign prostatic epithelium and primary cancer in all cases and in 98% of cases with lymph node metastases. Expression of PSMA wa s greatest in primary cancer for both percentage and intensity of immu noreactive cells. PSMA expression allows the identification of benign and malignant prostatic epithelium and may be a potentially valuable m arker in the treatment of patients with prostate cancer. UROLOGY 52: 6 37-640, 1998. (C) 1998, Elsevier Science Inc. All rights reserved.