Leptomeningeal fibroma.

Few cases of benign fibrous tumors have been reported in the central nervous system. Of the 9 cases in the literature only 1 was adjacent to the leptomeninges. We report a case of a fibroma of the leptomeninges of very low cellularity with calcified areas that had typical findings of a fibroma by electron microscopy. Immunophenotyping revealed unexpected positivity for S-100 and glial fibrillary acidic proteins. The histogenesis of this lesion may be a pluripotential cell, or the expression of these antigens may be induced by local factors in the central nervous system. The incidence of this unusual lesion is unknown, and ours is more typical of extracranial fibromas than the previously reported cases.