The WHO Grade I Collagen-forming Meningioma Produces Angiogenic Substances. A New Meningioma Entity.

Abstract Meningiomas arise from arachnoid cap cells, the so-called meningiothelial cells. They account for 20-36% of all primary intracranial tumours, and arise with an annual incidence of 1.8-13 per 100,000 individuals/year. According to their histopathological features meningiomas are classified either as grade I (meningiothelial, fibrous/fibroblastic, transitional/mixed, psammomatous, angiomatous, microcystic, secretory and the lympholasmacyterich sub-type), grade II (atypical and clear-cell sub-type) or grade III (malignant or anaplastic phenotype). A 62-year-old female patient presented to the hospital because of progressive obliviousness and concentration difficulties. In the magnetic resonance imaging (MRI) of the brain, an occipital convexity-meningioma was found in the left hemisphere, which was subsequently resected. Within the tumour tissue there were multiple spheroid precipitates, i.e. secretion products that turned out to consist of collagen. Part of the tumour cells displayed positive reactions for vasogenic substances, namely for vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR). Correspondingly, the diagnosis "WHO Grade I collagen-forming meningioma" seems to be most appropriate. The "WHO Grade I collagen-forming meningioma" reported herein produces collagen and angiogenic substances. To the best of our knowledge, no such entity has been reported on in previous literature. We propose this collagen-producing meningioma as a novel WHO grade I meningioma sub-type.