Metaplastic Meningioma Overspreading the Cerebral Convexity

Abstract

Meningioma is relatively common, benign, and extra-axial tumor accounting for about 20% of primary brain and spinal cord tumors. The World Health Organization (WHO) classified these tumors into Grade I (benign), Grade II (atypical), and Grade III (anaplastic) meningioma. Grade I meningioma which is slowly growing tumor and have some rare subtypes. Among them, metaplastic subtype is defined as a tumor containing focal or widespread mesenchymal components including osseous, cartilaginous, lipomatous, myxoid or xanthomatous tissue, singly or in combinations. We report a rare metaplastic meningioma overspreading nearly whole cerebral convexity from main extra-axial tumor bulk in the parietal lobe.

Keywords: Benign; Brain neoplasms; Meningioma, cerebral convexity; Pathology.

Fig. 1. Brain CT shows about 6.7×4.5 cm sized, low-density, broad dural based, and inhomogeneous enhancing mass with multiple calcifications in the left parietal region which is suggesting extra-axial tumor. Definite subdural lesion is not seen on the brain CT.

Fig. 2. Brain MRI shows extra-axial inhomogeneous enhancing tumor in the left fronto-parietal region. Bulky parietal mass shows low-signal intensity and the other flat subdural mass overspreading cerebral convexity shows iso-signal intensity on T1-weighted image (WI) (A). Inhomogeneous and homogeneous enhancements are seen in bulky parietal mass and flat subdural mass respectively (B). High-signal intensity in bulky parietal and flat subdural mass are seen on T2-WI (C). On fluid attenuated inversion recovery image, iso-signal intensity in the bulky parietal mass and high-signal intensity in the flat subdural mass are seen (D).

Fig. 3. On the cerebral angiograms, tumor staining via the left middle meningeal artery is seen.

Fig. 4. Operative findings. Bulky and soft tumor mass with multiple small cysts and calcifications are seen in the parasagittal space of left parietal lobe. Flat and rubbery tumor mass in the subdural space is overspreading the nearly whole cerebral convexity. These tumors are totally extra-axial. And the tumors were not infiltrated to the brain parenchyme.

Fig. 5. Pathologic findings. A: The tumor composed of plump, elongated cells with meningothelial features in syncytial arrangement. The nuclei are round to ovoid harboring fine chromatin and inconspicuous nucleoli. There is no evidence of mitosis or necrosis (hematoxylin-eosin staining, ×10). B: The areas of chicken-wire-like calcification and ossification are seen in several areas (hematoxylin-eosin staining, ×40). C: Lipomatous metaplasia and xanthomatous change are present (hematoxylin-eosin staining, ×100). D: The tumor cells show a low Ki-67 labelling index with about 1% (immunohistochemistry staining, ×40).