The patient underwent a T12-L1 laminectomy and subtotal removal of a sausage-shaped tan to pink, fleshy mass. The lesion was poorly defined from surrounding cord proximally. Microscopically, the specimen showed a heterogeneous tumor of moderate cellularity and plentiful perivascular lymphocytic infiltrates. Its border with normal spinal cord was indistinct and accompanied by reactive astrocytosis. The component cells were variable but could be readily divided into two subpopulations: smaller cells resembling glia with variable cytoplasm, eccentric round nuclei, clumped chromatin and indistinct nucleoli and a second group of larger cells resembling neurons with abundant basophilic cytoplasm, large vesicular nuclei and prominent nucleoli. The glial component was moderately pleomorphic and the neurons were often bizarre in their morphology, including binucleate examples. Numerous eosinophilic granular bodies were encountered. There were no mitotic figures.
Many of the smaller cells proved to be glial fibrillary acidic protein (GFAP) positive. The larger cells were characterized by expression of neuron specific enolase (NSE), neurofilament (NF) and synaptophysin (SYN). Many of these neurons also expressed nestin (anti-nestin antibody was a generous gift of R.D.McKay). MIB-1 labeling was very low (less than 1%).