Cystic papillary meningioma with subarachnoid dissemination: a case report and review of the literature.

Meningiomas usually present as benign tumors corresponding to WHO grade I. The development of the papillary variant of meningiomas with cyst formation in the central nervous system is extremely rare. We report a case of cystic papillary meningioma in a young female occurring in the lateral ventricle with invasion of brain parenchyma and dissemination of subarachnoid space. The tumor exhibits a marked peritumoral cyst, with contrast enhancement on magnetic resonance imaging (MRI) in accordance with type 2 of Zee's classification of cystic meningioma. Histologically, the tumor displays a classical perivascular pseudopapillary pattern with focal necrosis and subarachnoid space dissemination. Tumor cells are diffusely positive for epithelial membrane antigen (EMA) and vimentin, but lack immunoreactivity for cytokeratin (CK) and glial fibrillary acidic protein (GFAP). MIB-1 labeling is high, accounting for 5% of tumor focally. A diagnosis of primary intraventricular cystic papillary meningioma with subarachnoid space dissemination (WHO grade III) was made. To our knowledge, there is no report describing the radiological and histological characteristics of cystic papillary meningioma presenting in the lateral ventricle. In addition, the biological behavior and the clinical outcome of this tumor are also discussed.