Immunohistochemical localization of a prostatic secretory protein of 94 amino acids in normal prostatic tissue, in primary prostatic tumors and in their metastases.

Using the immunoperoxidase technique, we have studied in normal, hyperplastic and adenocarcinomatous prostates the tissue localization of an abundant 94 amino acid protein secreted by prostatic epithelial cells. In normal and hyperplastic prostates, strong immunoreactivity was found exclusively in glandular epithelial cells. No reaction was observed over the stroma. In well differentiated adenocarcinoma, the acinar cells were generally stained less intensely than in benign prostatic hyperplasia while in poorly differentiated tissue, strongly positive immunoperoxidase staining was found in some cancer cells scattered in the stroma. All prostatic cancer tissues examined (N = 21), with the exception of one, exhibited at least a few positive immunoreactive areas for the 94 amino acid secretory protein. In addition, immunoperoxidase staining was observed in lung and bone marrow metastases respectively in two patients with prostatic carcinoma. All other normal tissues and non-prostatic cancers studied to date were negative. These results suggest that this new marker could be a useful addition to prostatic acid phosphatase and prostate specific antigen.