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

An immunocytochemical method to localise prostate-specific antigen (PSA) in paraffin sections was used to establish the prostatic origin of both primary and metastatic tumours. 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 has now been applied diagnostically to tumour tissue resected from 21 patients. These neoplasms of the base and neck of the bladder could not be categorised as prostatic or urothelial in origin by clinical and endoscopic assessment or by conventional histopathology. In 11 patients such tumours were PSA-positive, indicating a prostatic origin. In two 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.