PRIMARY CENTRAL-NERVOUS-SYSTEM LYMPHOMAS IN IMMUNOCOMPETENT INDIVIDUALS - HISTOLOGY, EPSTEIN-BARR-VIRUS GENOME, KI-67 PROLIFERATION INDEX, P53 AND BCL-2 GENE-EXPRESSION

Epstein-Barr virus (EBV) has been detected in the large majority of HN -related primary central nervous system lymphomas (PCNSL) suggesting a pathogenetic role of the virus. Unlike HIV-related PCNSL, conflicting data exist with regard to the presence of EBV in non immunodeficiency -related (sporadic) PCNSL: For this reason, a population based materia l of 41 sporadic PCNSL was analysed for the presence of EBV genome (EB ER, BHLF) using RNA in situ hybridisation (RISH). Furthermore, the exp ression of the gene products of the bcl-2 oncogene and the p53 tumor s uppressor gene and the tumor growth fraction reactive with the monoclo nal antibody Ki-67 have been evaluated. All cases but two were EBV gen ome negative. In the two positive cases less than 5% of tumor cells sh owed EBER positivity. In contrast, more than 75% of cells morphologica lly belonging to the tumor-cell population stained positively for EBER in two cases of HIV related PCNSL. Immunostaining for the bcl-2 oncop rotein was positive in 28 (72%) of 39 cases examined. In most cases mo re than 75% of tumor cells showed cytoplasmic expression. Of 37 cases investigated for p53 expression, 21 (57%) stained positively. However, in the large majority of positive cases less than 10% of the neoplast ic cells stained. The percentage of Ki-67 positive cells ranged betwee n 10% and 80% with a mean of 50%. The expression of the p53 and bcl-2 oncoproteins and the growth fraction did not have any prognostic impac t. We conclude that the EBV genome is rarely detected in sporadic PCNS L, indicating that a pathogenetic role of EBV is unlikely. Like extrac erebral B-cell lymphomas a large fraction of PCNSL expresses the p53 a nd bcl-2 oncoproteins, a feature, however, which does not seem to have prognostic implications.