Myxoid Solitary Fibrous Tumor of the Central Nervous System

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Solitary fibrous tumors (SFTs) most commonly occur in the pleura, but may also occur in the central nervous system (CNS). Among the numerous cases of CNS SFT that have been reported , totaling to more than 220 cases, the myxoid SFT of the CNS has been the least recognized and most misleading sub-type. 1 Differential diagnosis from chordoid or myxo-chordoid meningioma, myxoid peripheral nerve sheath tumor, metastatic or primary low-grade fibromyxoid sarcoma, primary intracrani-al myxoma, and metastatic tumor from a cardiac primary tumor is therefore necessary. Here, we present a case of a myxoid SFT located in the tentorium cerebelli. A 45-year-old woman presented with headache, general weakness, and impaired vision. A magnetic resonance imaging scan revealed a lunulating, contoured, enhancing mass measuring 7.0×6.0×2.0 cm with hemorrhagic foci, located in the right posterior parietal and temporooccipital convexities. Under the diagnosis of meningio-ma, open craniotomy, right parietotemporooccipital, and subto-tal tumor removal was performed. Upon observation, many firm, rubbery, and bosselated tumor fragments, tan-white in color, were identified. The cut surface was relatively homogeneous, with a whitish fibrotic appearance and softer areas of gelatinous myxoid change, approximately 50%. Necrotic areas were not observed. Microscopic examination revealed a predominantly hypocellular area in the myxoid stroma, intervening with foci of a morphologically typical, densely cellular SFT with spindle cells and collagenous stroma (Fig. 1). In the hypocellular and myxoid areas, a proliferation of cytologically bland spindled cells was randomly arranged in a loose myxoid matrix, forming interconnecting strands, and resulting in degeneration. The neoplastic cells had oval to elongated nuclei, with evenly distributed chromatin, inconspicuous nucleoli, and scant pale cytoplasm. Immunohistochemically, the tumor cells showed a strong expression of CD34, vimentin, Bcl2 and CD99, but were negative for epithelial membrane an-tigen (EMA), pan-cytokeratin, and glial fibrillary acidic protein (GFAP). The Ki-67 labeling index was lower than 4%. On the basis of these findings, the final diagnosis was myxoid SFT. Myxoid SFT of the CNS is an extremely rare tumor and differential diagnosis may be difficult to achieve owing to confusion with several other myxoid spindle cell neoplasms. Indeed, myxoid SFT of the CNS must be differentiated from chordoid or myxo-chordoid meningioma, myxoid peripheral nerve sheath tumor, metastatic …