Immunocytochemical Localisation of Prostate‐specific Antigen: Specificity and Application to Clinical Practice

Abstract
An immunocytochemical method to localize prostate-specific antigen (PSA) in paraffin sections was used to establish the prostatic origin of both primary and metastatic tumors. The specificity of the technique was confirmed in 65 known primary (63 PSA-positive) and 17 metastatic prostatic carcinomas (16 PSA-positive). Thirteen non-prostatic primary carcinomas and a series of benign proliferative and malignant conditions which might be considered in the morphological differential diagnosis of prostatic adenocarcinoma were PSA-negative. The technique was applied diagnostically to tumor tissue resected from 21 patients. These neoplasmas of the base and neck of the bladder could not be categorized as prostatic or urothelial in origin by clinical and endoscopic assessment or by conventional histopathology. In 11 patients such tumors were PSA-positive, indicating a prostatic origin. In 2 further patients, the prostatic origin of lymph node secondaries was confirmed in the absence of a clinically apparent primary. The technique is a valuable adjunct to conventional histopathology.