A new subtype of meningioma

Three patients with small meningiomas presented with diffuse cerebral edema that was out of proportion to the size of tumors. All lesions were small a nd no brain invasion or unusual tumor vascularity or dural sinus involvemen t was noted in any of the three cases. Tumor material was subjected to conv entional and immunohistochemical stains. All three tumors showed benign men ingothelial components, prominent formation of hyaline inclusions (pseudops ammoma bodies), and striking vascular mural proliferation of small dark cel ls. All patients have remained asymptomatic without any evidence of tumor r ecurrence after a follow-up of 4-6 years. These tumors showed proliferation of pericytes in blood vessel walls and, therefore, represent a new subtype of meningothelial meningioma. In the study presented here, the location, s ize, histotype, and clinical findings that may influence the development of peritumoral brain edema are discussed in detail.