Fig. 3

Histopathological examination of the excised tumor. a Low-power view of the excised tissue with hematoxylin and eosin staining. On the periphery of the tumor tissue, cystic components were observed. b Middle-power view of the tumor tissue. Tumor cells were intermingled with hyalinized blood vessels. c-e High-power view of the tumor cells. The tumor cells were pleomorphic and harbored eosinophilic cytoplasm and hyperchromatic nuclei (c). A meshwork of fine fibers was observed in the acellular area, and cells with eosinophilic granular inclusions or hyaline bodies were observed (d). Lipofuscin granules showed various colors, from faint pinkish to dark brown (e). f, g Hyalinization was diffusely observed in the wall of the blood vessels and intra-tumoral matrix. h Scattered Rosenthal fibers were observed in the cerebellum surrounding the tumor. i-l Representative images of immunohistochemical analyses. Tumor cells were diffusely positive for S-100 protein (i) and focally positive for glial fibrillary acidic protein (j). Tumor cells were negative for Olig2 (k). The Ki-67 labeling index was less than 1% (l). Scale bars: 1 mm (a), 200 μm (b, g), 100 μm (f, h-j), and 50 μm (c-e, k, l)