PROSTATE INHIBIN PEPTIDE (PIP) IN PROSTATE-CANCER - A COMPARATIVE IMMUNOHISTOCHEMICAL STUDY WITH PROSTATE-SPECIFIC ANTIGEN (PSA) AND PROSTATIC ACID-PHOSPHATASE (PAP)

Prostate inhibin peptide (PIP) is a polypeptide synthesized by the pro state gland that is involved in prostatic growth and differentiation. The objective of this study was to evaluate PIP as an immunocytochemic al marker for prostatic adenocarcinoma (PCA) by comparing it with PSA and PAP. A total of 71 cases of primary PCA and 5 cases of metastatic PCA were studied. Primary tumors were specially selected to include a disproportionate number of high-grade tumors. The distribution of case s by Gleason score was 2-5, 14 cases; 6-7, 24 cases; and 8-10, 33 case s. Four metastases were to bone (decalcified tissue) and one to soft t issue. All 71 cases of primary PCA stained positively for the three an tibodies tested, with none demonstrating obvious superiority, although individual case variability was seen. In one bone metastasis, stainin g for PSA was negative, with both PAP and PIP giving positive results. All non-prostatic carcinomas tested were negative. These results indi cate that PIP is as sensitive and specific an immunohistochemical mark er as PSA and PAP in untreated prostate adenocarcinomas. Further, the androgen-independent nature bf PIP may give it an advantage over PSA/P AP in tumors exposed to androgen ablating agents.