Immunohistochemical diagnosis of the metastasizing prostatic carcinoma

Metastases of 47 known prostatic carcinomas were subjected to the unlabeled immunoperoxidase procedure to localize prostate acid phosphatase (PAP) and prostate-specific antigen (PSA). PAP was found in 64% and PSA in 78% of bone marrow, lymph node, lung and liver metastases investigated. There was no significant difference between the intensity of staining in primary and metastatic neoplasms. Staining of PAP and PSA was found to be less intense in poorly differentiated metastases of prostatic adenocarcinomas. The data suggest that the demonstration of PAP and PSA is a practical and sensitive test for determining the prostatic origin of a clinically and histologically unclassifiable metastasis.