Expression of epithelial and extracellular matrix protein markers in meningiomas

In an attempt to characterize the dual mesenchymal and epithelial differentiating potential of meningiomas, cryostat sections from 50 meningiomas of diverse histological subtypes were examined immunohistochemically with a panel of markers for epithelial and mesenchymal differentiation. The overall positivities were: keratins 50%, epithelial membrane antigen 94%, human milk fat globules 38%, carcinoembryonic antigen 4% (secretory meningiomas only), desmoplakins 64%, collagen I 82%, procollagen I 96%, collagen III 74%, collagen IV 60%, laminin 54%, fibronectin 98% and vimentin 98%. Such production of keratins was not found in many previous immunohistochemical analyses of meningiomas with paraffin sections. The extracellular matrix proteins were present in a pericellular distribution suggestive of their being produced by the tumour cells. The potential of dual epithelial and mesenchymal differentiation in meningiomas was further examined in seven cases established on short-term cultures. Morphologically, subcultured tumour cells resembled fibroblasts and in five cases revealed similar epithelial and mesenchymal immunohistochemical profiles as for direct tumour immunostaining. In two cases, cells from the primary cultures revealed a fine skeleton of intercellular matrix proteins stainable by immunohistochemical methods, providing further proof that meningioma cells possess the capability to elaborate extracellular matrix proteins, a major mesenchymal function akin to that of fibroblasts.