Multifocal neurocytoma/gangliocytoma with extensive leptomeningeal dissemination in the brain and spinal cord.

This report describes an unusual neuronal tumor detected at the autopsy of a 17-year-old boy. The tumor showed multifocal parenchymal involvement with extensive leptomeningeal dissemination. The intraparenchymal lesions were small and located mainly in the subpial region of the cerebrum, cerebellum and spinal cord. Leptomeningeal dissemination was particularly pronounced at the base of the brain and around the spinal cord and presumably took place during the relatively long clinical course. The tumor was composed of small round cells and ganglion-cell-like cells. Only neuronal differentiation, as represented by immunostaining with antisynaptophysin antibody and the presence of dense-core vesicles in the cytoplasm, was evident in both types of cells. The small round cells appeared to exhibit the features of small, relatively mature neurons rather than those of neuroblasts. Moreover, our results suggested maturation from small round cells to ganglion-cell-like cells. The tumor appears to be related to gangliogliomas or dysembryoplastic neuroepithelial tumors, and we have chosen the term neurocytoma/gangliocytoma for the unusual lesion.