H&E sections of the tumor operated in 1994 showed a moderately cellular glial neoplasm. Some areas were composed of piloid astrocytes and displayed few Rosenthal fibers (Fig. 3A). Sometimes larger multinuclear cells were present (Fig. 3B). The regions near the ventricle were composed of loosely arranged piloid cells and large glial cells with one or more nuclei (Fig. 3C) and a broad glial fibrillary acidic protein (GFAP)-positive cytoplasm (Fig. 3D). Areas immediately at the ventricle site ('V' in Fig. 3C and Fig. 3D) showed five or six 'layers' of densely packed smaller astrocytic cells with shorter processes and only slight GFAP-immunoreaction. Mitoses, necroses and endothelial proliferations were absent.
The biopsy of one of the ventricular tumor disseminations in 1998 revealed histological and immunohistochemical features which were very similar with the initial resection specimen. The density of capillaries was however higher (Fig. 8A). The smaller neoplastic astrocytes which formed a 'layer' at the ventricle site were also demonstrable in the tumor spreadings (Fig. 8A). They could sometimes be found in the ventricular space without connection to the other tumor cells (Fig. 8B, arrow). As in 1994, no histologic signs of anaplasia or malignancy could be found. Mitoses were absent. The Ki67-positivity was very low, especially in the densely packed cells in close vicinity to the ventricle (not shown). Cebrospinal fluid cytology revealed no anaplastic cells.