Contributed by Jakob Matschke1, Manfred Westphal2, and Katrin Lamszus2
1Institute of Neuropathology and 2Department of Neurosurgery,
University Hospital Hamburg-Eppendorf, Hamburg, Germany
Published on line in November, 2004
This 63-year-old woman presented with a history of continuously aggravating lower back pain, sometimes radiating down the back of her thighs, of approximately 4 months duration. In the weeks preceding the initial clinical evaluation, she experienced urinary urge incontinence. There were no pareses or sensory disturbances. The other aspects of the clinical history were completely unremarkable.
T1-weighted magnetic resonance imaging of the spinal cord revealed a sharply-delineated, partly cystic intradural mass with inhomogenous contrast-enhancement at the level of the cauda equina (Fig. 1). T2-weighted imaging showed serpentine structures at the upper pole, corresponding to ectatic vessels (Fig. 2). Axial sections revealed that the tumor filled the entire spinal canal but had not caused bony erosion (Fig. 3). An ependymoma of the cauda equina was suspected and the patient was operated.
Intraoperatively, the cranial end of the tumor was found to be attached directly to the conus. A single arterial feeder was present between the lower end of the conus and the mass, and was accompanied by several ectatic veins. The oval-shaped tumor was ensheathed by a delicate collagen capsule and displayed a soft, homogenously brown-reddish cut surface. The tumor mass was removed in toto.
At low magnification, the tumor appeared moderately cellular, relatively monomorphic, and contained several areas with cystic structures (Fig. 4). At higher magnification, regions composed of small uniform cells were found to be interrupted by areas of diminished cellularity. In addition, the tumor cells often formed perivascular pseudorosettes with tumor cell processes arranged radially around blood vessels (Fig. 5). In several regions, structures resembling ependymal canals were identified that were composed of columnar cells lined around a central lumen (Fig. 6). Occasionally, hemosiderin deposits were found in the vicinity of blood vessels (not shown). The tumor cells possessed small, round-to-oval, isomorphic nuclei with sharply delineated nuclear membranes, delicate stippled chromatin and small, inconspicuous nucleoli; up to 2 mitoses per 0,19 mm2 visual field were identified (Fig. 7, arrows). Interspersed between the predominating small-cell tumor component, occasionally mature ganglion cells with large vesicular nuclei and prominent nucleoli could be discerned; the ganglion cells were arranged either in small clusters or scattered as single cells (Fig. 8, arrows). In addition, larger islet-like fields composed of cells displaying a phenotype transitional between the small tumor chief cells and mature ganglion cells were found (Fig. 8, islet marked by arrowheads). Reticulin staining revealed that aggregates of tumor cells were circumscribed by a delicate connective tissue framework (Fig. 9).
Immunohistochemically, both the ganglionic cells and the small tumor chief cells were strongly immunoreactive for neurofilament (Fig. 10) and synaptophysin (Fig. 11), as well as neuron-specific enolase and chromogranin (not shown). GFAP expressing sustentacular cells were clustered in the vicinity of small nests of ganglion cells, and were also scattered between the small chief cells (Fig. 12). Many tumor cells displayed perinuclear immunoreactivity for cytokeratin, and especially the columnar cells that surrounded lumina reminiscent of ependymal canals were strongly cytokeratin-positive (Fig. 13). The MIB-1 labeling index focally reached 5% (not shown). Ultrastructurally, numerous perinuclear dense-core granules were detected in the tumor cells (Fig. 14).