Microcystic variant of meningioma: a light-microscopic and ultrastructural study.

Meningiomas occasionally show small areas in which the cells are stellate with slender processes surrounding microscopic spaces, giving a lace-like appearance to the tissue. In the case of a 52-year-old woman with a tumor rising from the falx, virtually the entire tumor was composed of lacy reticulated tissue. Most of the tumor cells had processes that stained blue with phosphotungstic acid hematoxylin, suggesting the appearance of a glioma. However, electron microscopy showed that the extracellular space was extensive, and the tumor cells had long cytoplasmic processes which formed interdigitations with one another. Desmosomes were numerous. The immunoperoxidase method for glial fibrillary acidic protein gave negative results. On the basis of these histologic features, we suggest that this tumor was a microcystic variant of meningioma.