A case of tanycytic ependymoma arising from the cerebral hemisphere.

We report a rare case of tanycytic ependymoma arising from the cerebral hemisphere. A 59-year-old man was admitted to our hospital because of the incidental detection by MRI of a tumor lesion in the right temporooccipital paratrigonal region. The mass showed low-to iso-intensity on T1-weighted images and high intensity on T2/proton-weighted images. Partial resection was performed using a transsulcal approach to avoid compromising the visual field. Most of the tumor cells showed elongated spindle shapes arranged in dense fascicles. A few true ependymal rosettes and perivascular pseudorosettes were visible. The tumor cells were positive for GFAP, S-100, and vimentin, but negative for synaptophysin, EMA, and keratin. The MIB-1 labeling index was approximately 1%. Ultrastructurally, the tumor cells had ependymal cell features, such as microvilli and cilia. From these findings, a pathological diagnosis of tanycytic ependymoma was made.