A case of anaplastic clear-cell ependymoma presenting with high erythropoietin concentration and 1p/19q deletions

We describe a 19-year-old woman with onset of epileptic seizure, and a small mural nodule and multicystic lesions with severe brain edema located in the right frontal lobe. At surgery, the tumor and a clear margin was removed, and symptoms improved postoperatively. Extended local radiotherapy (60 Gy) was performed. Histopathological examination revealed oligodendroglioma-like tumor cells with a perinuclear halo. The tumor cells extended processes toward CD34-positive proliferating vessels, which resemble a basement membrane. These proliferating vessels formed a tumor membrane so that there was a clear margin between the tumor and brain tissue. Tumor cells were positive for epithelial membrane antigen in a dot-like pattern. MIB-1 staining index was 50.6%. Electron microscopy showed cilia and zipper-like junctions, and anaplastic clear-cell ependymoma grade III was diagnosed. A characteristic of the case was formation of a tumor membrane by proliferating tumor blood vessels. Fluorescence in situ hybridization showed 1p/19q deletions, and the concentration of erythropoietin in the cyst fluid was abnormally high, at 1,859.4 mIU/ml. Erythropoietin and erythropoietin receptors were verified with immunohistochemical staining.