Cervical cord ependymoma with numerous microrosettes

Abstract

"Microrosette ependymoma," which is ependymoma with numerous microrosettes throughout the tumor, has rarely been reported. We describe an autopsy case of cervical cord ependymoma with two unusual features: the presence of numerous microrosettes and the formation of trabecular architecture. The tumor originated in the C2 segment of a man aged 23 years and gradually expanded over the following 15 years and 10 months until the entire cervical cord was involved. Beside the low grade of malignancy, the tumor cells exhibited a strong tendency to form microrosettes and trabecular architecture, which formed many perivascular pseudorosettes. The microrosettes mostly consisted of only two or a few more cells, in the absence of large rosettes. Thus the constituent cells were those forming perivascular pseudorosettes. Electron microscopy and immunohistochemistry characterized the ependymal properties of the microrosettes, whose lumina frequently contained fibril bundles similar to those of the Reissner's fiber fibrils, in addition to cilia and microvilli. The pathogenesis of the occurrence of numerous microrosettes is unknown; however, a defect in the mechanism of regulation of rosette formation and enlargement is the most likely explanation.