[A case of clear cell meningioma originating from the cerebellar tentorium]

We report herein on a case of clear cell meningioma originating from the cerebellar tentorium, surgically treated by occipital transtentorial approach (OTT). A 67-year-old woman was admitted to our hospital in September, 1996, complaining of gait disturbance. MRI revealed an isointense mass on T1 and T2 WI, clearly enhanced with gadolinium in the right upper cerebellum originating from the tentorium. A left vertebral angiogram showed tumor stain from the right superior cerebellar artery. The tumor was subtotally removed by OTT on September 24, 1996. Gamma knife radiosurgery was performed for regrowing tumor 6 months after surgery. Histological examination revealed that the tumors were composed of sheets of clear, glycogen-rich cells and lobulated by thin connective tissues. There were no malignant findings, but some tumor cells had infiltrated into the cerebellar cortex. Immunohistochemistry showed that tumor cells were positive for EMA and vimentin, but negative for keratin. MIB-1 staining index was 7.02%. From these findings, this case was diagnosed as a typical clear cell meningioma originating from the cerebellar tentorium. From a review of the literature including our case, clear cell meningioma may be clinicopathologically malignant, so careful follow-up will be necessary.