Ganglion-cell tumor of the filum terminale: immunohistochemical characterization.

A case of an unusual spinal neuronal tumor is described in a 36-year-old woman presenting with a buttock pain. The spinal tumor was fully characterized by neuroradiological means, and in particular MRI was of significant value in delineating the extension of the tumor within the spinal canal and its exophitic growth pattern. Pathologically, a well circumscribed tumor originating from the intradural filum terminale characteristically comprised both large and small cells, resembling mature and immature neuronal cells, respectively. In addition, two neuronal markers, i.e., chromogranin A (CGA) and neuron-specific enolase (NSE), and other markers such as glial fibrilary acidic protein (GFAP), S-100 protein, HNK-1, tyrosine hydroxylase and beta 2-microgloblin were investigated immunohistochemically. We found that both neuronal cells expressed immunoreactivity for CGA and NSE, and small neuronal cells showed more intense CGA immunoreactivity, indicating an earlier stage of neuronal differentiation. Weakly positive immunoreactivity for HNK-1 was also demonstrated in small neuronal cells, consistent with evidence of maturation along a neuronal differentiation. From these findings a pathological diagnosis of ganglioneuroma was made. This unique group of ganglion-cell spinal tumors is reviewed in the literature and differential diagnosis and immunohistochemical features are discussed.