Investigation of carcinoma in situ cells of testis by quantification of argyrophilic nucleolar organizer region associated proteins (AgNORs)

The silver staining which specifically stains argyrophilic proteins (AgNORs) in interphase nuclei was applied to paraffin sections of 24 testicular specimens with carcinoma in situ (CIS). AgNOR area per nucleus was quantified by a computerized image analyser. Significant quantitative differences were found between CIS, Sertoli cells, and spermatogonia (P = 0.0001), with median values of 10.3, 2.8, and 1.4 microns2 in the three cell types, respectively. A Sertoli cell index (SCI), defined as the ratio between AgNORs in CIS or spermatogonia and Sertoli cells, was shown to be significant in the differential diagnosis of CIS cells from spermatogonia when 1.0 was used as the cut-off value (CIS > 1; spermatogonia < 1). Furthermore, CIS associated with non-seminoma was found to have a significantly higher level of AgNORs than CIS associated with pure seminoma (P < 0.01), indicating that subclonal variation in transformation potential might be present within morphologically identical CIS of the testis. It remains to be seen whether quantification of AgNORs in isolated CIS could be used to predict transformation of CIS into seminoma or non-seminoma.