THE AGNOR TECHNIQUE, PCNA IMMUNOHISTOCHEMISTRY, AND DNA-PLOIDY IN THEEVALUATION OF CHOROID-PLEXUS BIOPSY SPECIMENS

The histologic distinctions between normal choroid plexus and choroid plexus papilloma and between choroid plexus papilloma and choroid plex us carcinoma are sometimes difficult. The authors performed the silver nucleolar organizer region (AgNOR) technique, immunohistochemistry fo r proliferating cell nuclear antigen (PCNA), and DNA ploidy analysis b y flow cytometry on 9 samples of normal choroid plexus, 8 papillomas, and 13 carcinomas to evaluate whether these techniques can aid in thes e differential diagnoses. Significant differences were found in the me an AgNOR count between normal choroid plexus (1.35 +/- 0.11) and choro id plexus papillomas (2.42 +/- 0.81) (P < 0.001), but not between chor oid plexus papillomas and carcinomas. In the normal choroid plexus, Ag NORs were smooth and round; in the papillomas and carcinomas, however, they varied in size and shape. Compound AgNORs were commonly present in the tumors but were essentially absent in controls. Antibody to PCN A did not stain normal choroid plexus cells (except for focal staining in one sample of normal choroid plexus adjacent to a carcinoma) but s tained many papilloma and carcinoma cells. DNA ploidy analysis demonst rated aneuploidy in some papillomas and carcinomas but could not be us ed for the distinction of normal choroid plexus from papillomas. These results suggested that the AgNOR technique and PCNA immunohistochemis try could be used to distinguish normal choroid plexus from choroid pl exus papilloma in small, diagnostically difficult biopsy specimens.