Proliferating cell nuclear antigen expression in brain tumors, and its prognostic role in ependymomas: an immunohistochemical study.

Proliferating cell nuclear antigen (PCNA)/cyclin is currently often investigated immunohistochemically in tumors as a marker of cell proliferation, but many problems remain open concerning its reliability as a prognostic factor. PCNA has been studied in a series of 123 brain tumors using the monoclonal antibody PC10. A clear intra- and inter-tumor variability of PCNA-positive nuclei has been found, but taking into account the tumor areas with the highest number of positive nuclei, a positive correlation between this number and the histological malignancy of tumors has been demonstrated. The staining intensity of nuclei was variable; very-intensely positive nuclei, counted separately, are hypothesized to represent nuclei in S-phase of the cell cycle. In ependymomas the investigation included a quantitative statistical analysis. The number of PCNA-positive nuclei correlated with cell density and mitotic index, but only very intensely positive nuclei showed a significant statistical correlation with survival. In spite of the many possibilities of wrong interpretation of PCNA expression, the most important of which is its deregulation, the method is useful in the practice for prognostic purposes. Its important advantages are the possibility of a retrospective application and a visual analysis of the proliferation potential of tumors.