Atypical Subependymoma of the Spinal Cord: Ultrastructural and Immunohistochemical Studies.

A 76-year-old woman with a 2-year history of progressive weakness of the left arm and leg underwent a laminectomy for an intradural, extramedullary, pedunculated subependymoma involving the meninges and spinal nerve roots at C7-T1. Eight months later, another operation was necessary for an intramedullary neoplasm at C3-T4. This latter tumor consisted of small, poorly developed cells, large atypical astrocytes, and ependymal cells. Neither ependymal rosettes nor papillary formations were present. Ultrastructural studies showed some features of ependymal differentiation of the large "astrocytic" cells. This case illustrates an unusual pattern of extramedullary and intramedullary presentations of subependymoma and a spectrum of cellular differentiation of neoplastic subependymal glia.