Clinical presentation, immunohistochemistry and electron microscopy indicate neurofibromatosis type 2‐associated gliomas to be spinal ependymomas

Neurofibromatosis type 2 (NF2) is a hereditary tumor syndrome. The hallmark of NF2 is bilateral vestibular schwannoma. In addition, glioma is one of the diagnostic criteria of NF2. In this retrospective study the clinical presentation and histopathological features of 12 spinal gliomas from NF2 patients were assessed. Ten tumors were previously diagnosed as ependymomas and two as astrocytomas. However, upon re-evaluation both astrocytomas expressed epithelial membrane antigen in a dot-like fashion and in one case it was possible to perform electron microscopy revealing junctional complexes and cilia typical for ependymoma. The findings suggest that NF2-associated spinal gliomas are ependymomas. Based on the fact that NF2-associated gliomas are almost exclusively spinal and that no NF2 mutations have been found in sporadic cerebral gliomas, we suggest that "glioma" in the current diagnostic criteria for NF2 should be specified as "spinal ependymoma".