Contributed by A Tauziede-Espariat, MD1, H Adle-Biassette, MD, PhD1, A Simonneau, MD2, JM Guinebretiere, MD, PhD3, M Polivka, MD1
1Department of Pathology, Lariboisiere Hospital, 75475 Paris, France
2Department of Neurosurgery, Rothschild Foundation, 75019 Paris, France
3Department of Pathology, Rene Huguenin Hospital, 92210 Saint-Cloud, France
A 50-year-old man was followed for 4 years for a radiological diagnosis of meningiomas of the falx cerebri. He was admitted for an evaluation of the mass that had slightly increased in the last year prior to this presentation. General examination disclosed nothing. Computed tomography showed a large hypodense well-circumscribed mass attached by a broad base to the falx cerebri (Figure 1a). On MRI of the head, the tumor measured 3.5 cm and appeared hypointense on T1-weighted images and hyperintense on T2-weighted images. It was uniformly enhanced by Gadolinium contrast injection (Figure 1b) and hyperinstense on T2-Flair (Figure 1c). There was no parenchymal abnormality. The radiologist interpreted the imaging as suspicious for a meningioma. Due to the recent enlargement of the tumor, a total resection was performed. Intra-operatively, the lesion was defined by the surgeon as a lesion with a dural-based attachment suggesting a meningioma.
Histopathological examination evidenced a well-delineated myxoid lesion adhering to the meninges without infiltration (Figure 2). It was lobulated by thin fibrovascular septa fibrous (Figure 3). In this myxoid matrix, some mast cells, spindle cells and fibroblasts intertwined with lymphocytes (Figures 4 and 5). There was no atypia, no mitotic activity and no necrosis (Figures 4 and 5). On immunohistochemical analysis, there was no staining for GFAP, cytokeratins, muscular markers (smooth muscle actin, desmin) and nuclear receptor of progesterone. Mast cells were immunoreactive for epithelial membrane antigen (EMA) and S-100 protein. Fibroblasts and endothelial cells were immunostaining by CD34. MIB-1 was low (inferior to 1%). What is your diagnosis?