Hemangiopericytoma of the meninges: a clinicopathologic and immunohistochemical study.

This clinicopathologic study concerns 15 cases of hemangiopericytoma of the meninges (so-called hemangiopericytic meningioma) among approximately 300 examined cases. Ages of the patients at the first surgery ranged from 25 to 67 years, with a median of 44 years. According to follow-up information, 9 of the 15 died between 1 year and 15 years after the initial treatment. Histologically, the tumor was indistinguishable from the hemangiopericytomas in other tissues and was characterized by a homogeneous vascular pattern, a uniform cell population and a wide range of cellular anaplasia. The presence of prominent mitotic activity suggested a highly active biological behavior. Immunohistochemical analyses for epithelial membrane antigen (EMA) were done in 35 various meningiomas, 12 meningeal hemangiopericytomas, and three extracranial hemangiopericytomas. Most of the meningiomas of meningotheliomatous, transitional, fibroblastic, papillary, angiomatous, and anaplastic types showed a positive immunoreactivity for EMA, while all of the meningeal hemangiopericytomas and extracranial hemangiopericytomas examined were negative for EMA. Our immunohistochemical study may support the concept that the meningeal hemangiopericytoma is composed of poorly differentiated cells which may originate from a perivascular mesenchymal cell of the meninges but not from the arachnoidal cap cell.