Enhancing gliotic cyst wall with microvascular proliferation adjacent to a meningioma.

Cystic meningiomas are uncommon. Contrast enhancement of the cyst wall of peritumoral cysts on radiological imaging is generally thought to indicate that the wall contains tumor cells. The authors present a patient with a peritumoral cyst that enhanced despite the absence of tumor cells. Histological analysis demonstrated a gliotic cyst wall with numerous microvascular proliferations (MVPs) adjacent to a mixed transitional and angiomatous/microcystic meningioma. Immunoreactivity for vascular endothelial growth factor (VEGF) and its receptor, flt-1, was observed in the endothelial cells of both intratumoral vessels and cyst wall MVPs. Immunoreactivity for tenascin-C was strongly observed within and around the vascular wall of MVPs and in gliotic tissue adjacent to the meningioma. These changes are unusual in the peritumoral brain parenchyma of a slow-growing convexity meningioma and the MVPs may account for the atypical contrast enhancement of the cyst wall despite the absence of tumor cells.