Two cases of nondura-based clear cell meningioma of the cauda equina.

Clear cell meningioma is a rare disorder. We report two cases of nondura-based clear cell meningioma of the cauda equina, one in a 24-year-old male and the other in a 19-year-old female. Both patients had complained of numbness and spontaneous pain in the lower back and limbs for several months. Magnetic resonance imaging and computed tomography scanning revealed an intradural tumor in the cauda equina in each case. At surgery, a neurilemoma was suspected, because each of the tumors had displaced nerve roots and had attached to one of the nerve roots without any adherence to the dura. Light microscopy revealed that both tumors were well-demarcated with a thin capsule and consisted mainly of clear, glycogen-rich, polygonal cells with vague whorl formations, and of copious deposits of hyalinized blocky collagen in the stroma and perivascular areas. The neoplastic cells were immunopositive for vimentin and epithelial membrane antigen, but immunonegative for S-100 protein and chromogranin A. Positive nuclei for MIB-1 were very few in both cases, and PCNA-labeling indices were 12.1% and 24.7%, respectively. No local recurrence has been seen for 61 months and for 52 months, respectively.