[Metaplastic meningioma with cartilaginous differentiation]

A meningioma with cartilaginous areas is described. The tumour arose in the region of the right sphenoid wing in a 74-year-old woman. Histologically, it showed large areas of a typical meningothelial meningioma, among which numerous cartilaginous islands and some chondroid regions, obviously of intermediate (meningothelial/cartilaginous) differentiation, could be seen. Cartilaginous tumour areas showed lower MIB1-labelling indices than typical meningioma regions, where an increased proliferative activity was seen focally. The current WHO classification lists such tumours as metaplastic meningiomas, reflecting the potential of meningioma cells for mesenchymal differentiation. Metaplastic meningiomas may show different metaplasias (xanthomatous, osseous, lipomatous, cartilaginous, etc.). Extensive cartilaginous metaplasias are very uncommon. Identification of typical meningioma areas is the key for the diagnosis of this meningioma variant.