An ultrastructural and immunohistochemical study of extracellular matrix in meningiomas.

Extracellular matrix of meningiomas was studied by light and electron microscopy with the aid of immunohistochemical techniques. Special attention was paid to the distribution of type I, III, IV, V collagens and laminin with a comparison between meningothelial and fibroblastic types. Connective tissue fibers and basement membrane were not found among the tumor cells in the meningothelial type, but were found in the fibroblastic type. The immunolocalizations were consistently demonstrated extracellularly, but were not within the cytoplasm. Type I, III and V collagens were usually demonstrated in the fibrous septum in the meningothelial type, while they were localized among the tumor cells in the fibroblastic type. Furthermore, type IV collagen and laminin were demonstrated within the vascular walls or around the syncytium in the meningothelial type, while they were localized among the tumor cells in the fibroblastic type. In both types the expression of type IV collagen and laminin was closely related to the distribution of basement membrane. Although meningothelial and fibroblastic meningiomas showed quite different distribution of extracellular matrices, the profile of collagen types expressed by these two basic types was essentially the same. The cellular derivation of meningiomas was discussed with particular attention to the structure of human arachnoid villi and meninges.