PROLIFERATING CELL NUCLEAR ANTIGEN AND NUCLEOLAR ORGANIZER REGIONS INCNS TUMORS - CORRELATION WITH HISTOLOGICAL TYPE AND TUMOR GRADE - A COMPARATIVE-STUDY OF 82 CASES ON PARAFFIN SECTIONS

We investigated the expression of proliferating cell nuclear antigen ( PCNA) and the number of nucleolar organizer regions (NORs) in 82 cases of CNS tumors. PCNA is a nuclear protein maximally elevated in the S phase of the cell cycle and recognized immunohistochemically in paraff in sections by the monoclonal antibody PC-10. On the other hand, NORs are loops of DNA that carry the rRNA genes and can be demonstrated in paraffin sections using an argyrophilic method (AgNORs). The present s tudy shows a significant correlation of PCNA index and of AgNOR number with the histological grade (PCNA: I versus II, p < 0.01; II versus I II, p < 0.01; and III versus IV, p < 0.05; AgNORs: I versus II, p < 0. 001; II versus III, p < 0.05- and III versus IV, p < 0.001). Higher va lues of PCNA index (0.01 < p < 0.05) were found in recurrent tumors. M etastatic carcinomas were characterized by high PCNA indices and AgNOR numbers, similar to grade IV tumors, whereas in CNS lymphomas the mal ignancy grade was reflected in PCNA indices and AgNOR numbers. A wide range of PCNA and AgNOR values has been observed within each histologi cal type and grade, probably reflecting variations in the biological b ehavior, but little overlap in PCNA values was present between grades II and III. The latter finding might be of importance in distinguishin g between low- and high-grade CNS tumors. The linear regression coeffi cient between PCNA index and AgNOR number was excellent (0.91). We sug gest that PCNA and AgNORs may be successfully applied in routine mater ial to assess the growth potential of CNS tumors. Their prognostic val ue, however, must be validated with clinical studies.