Meningioangiomatosis: an immunocytochemical study.

Meningioangiomatosis (MA) is a rare malformative lesion of the central nervous system. It has generally been thought that the main cells forming this lesion are derived from arachnoidal cap cells. We report a case of MA in which histochemical, immunoperoxidase and electron microscopic studies did not support a meningothelial origin of this lesion. Rather, the lesion in this case appears to be a vascular malformation with the dominant cells being fibroblastic, derived from vessel walls; however, their origin from arachnoid cap cells that differentiated into fibroblast-like cells could not be totally ruled out. Residual neurons within the lesion contained neurofibrillary tangles with ultrastructural and immunostaining properties identical to those seen in Alzheimer's disease except for the absence of A4 amyloid.