Perivascular elastic fibers: a diagnostic feature of ependymoma.

To assess the diagnostic potential of perivascular elastic fiber detection as an indicator of ependymoma, the authors performed ultrastructural studies on a large series of pediatric brain tumors. Elastic fibers were demonstrated by electron microscopy in 38 of 50 (76%) ependymomas, 2 of 25 (8%) choroid plexus tumors, 0 of 100 (0%) medulloblastomas, and 0 of 100 (0%) astrocytomas. In some poorly differentiated examples, elastic fibers were initially the sole indicator of ependymal differentiation. The authors conclude that the sensitivity and specificity of this feature is sufficient to render demonstration of perivascular elastic fibers a useful diagnostic indicator of ependymoma.