Malignant (anaplastic) transformation of orbital clear cell meningioma

A 69-year-old woman with a history of a previously resected right sphenoid wing meningioma and radiation presented with a 4-month history of a rapidly progressive right orbital swelling. MRI revealed a sphenoid wing mass extending in the right orbit and depressing the right globe. An incisional biopsy revealed a clear cell meningioma with anaplastic features. Histopathologic examination showed that the tumor was composed of sheets of polygonal cells with clear cytoplasm consistent with clear cell meningioma. Nuclear atypia with a high mitotic activity was also evident; thus, the tumor was classified as anaplastic. Clear cell meningioma is a rare form of meningioma usually located in the cerebellopontine or spinal cord areas.