Computer-assisted microscope analyses of Feulgen-stained nuclei were used to quantitatively describe the chromatin pattern and to determine the DNA ploidy level in a series of 70 cases including 46 low-grade (benign) ependymomas, 17 anaplastic (malignant) ependymomas, 3 choroid plexus papillomas (benign) and 4 choroid plexus carcinomas (malignant). While the quantitative description of the chromatin pattern was carried out by means of 14 morphonuclear parameters relating to geometric, densitometric and textural features, the DNA ploidy level was assessed by means of DNA histogram typing. Of these 70 cases, proliferative activity was assessed on 24, for which tissue was still available after the digital cell image analyses. This assessment was carried out by means of the determination of the immunohistochemical MIB-1 staining relating to the Ki-67 antigen. The results show that the determination of morphonuclear characteristics did not make it possible to distinguish between ependymal and choroid plexus tumours. Furthermore, neither the computer-assisted microscope analyses of morphonuclear characteritics nor the DNA ploidy level determination made it possible to distinguish between low-grade and anaplastic ependymomas. In sharp contrast, the determination of proliferative activity by means of the Ki-67 antigen immunohistochemical staining enabled such a distinction to be made.

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