Cerebellar papillary meningioma in a 3-year-old boy: the usefulness of electron microscopy for diagnosis.

We report one case of papillary meningioma located in the posterior fossa in a 3-year-old boy. Despite a gross total resection, a major recurrence occurred 6 months later that was operated on. Eight months later, another recurrence was observed with intracranial metastases and dissemination throughout the cerebrospinal fluid. The tumor had a papillary architecture more obvious in the recurrence. Areas of necrosis were numerous. Tumor cells had large clear atypical nuclei. Many mitotic figures were seen and Ki-67 labeling index was high. The tumor cells were immunoreactive for vimentin and polysialylated neural cell adhesion molecule only, ruling out a diagnosis of ependymoma or medulloblastoma. Diagnosis of meningioma was done by electron microscopy, which showed interdigitating cytoplasmic processes and cell junctions. Cytogenetic study revealed unusual karyotypic abnormalities.