PMC9177164_01
Preoperative (A-D) and postoperative (E, F) magnetic resonance images. Axial T1 weighted (A) and T2 weighted images with broad perifocal edema (B). Contrast-enhanced axial (C) and coronal (D) images suggest tumor attachment to the convexity dura mater, but intraoperative findings confirmed that the tumor originated from the falx near the superior sagittal sinus. Postoperative images (E, F) show the total resection of the tumor.
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The tumor demonstrated hypointensity and hyperintensity on T1 and T2 weighted images, respectively, with broad edematous changes in the surrounding brain parenchyma (Fig. 1A, B). Further images showed a homogeneously enhanced extra-axial tumor with possible parasagittal attachment to the dura mater (Fig. 1C, D), suggesting a wide range of radiological diagnoses, including meningioma, hemangiopericytoma/solitary fibrous tumor, ependymoma, and pleomorphic xanthoastrocytoma. Nine months after the resection, the magnetic resonance (MR) images revealed no tumor recurrence (Fig. 1E, F).
Pathology of the resected specimen. Hematoxylin and eosin staining (A) revealed that the tumor comprised a multilobulated structure with solid hypercellular (B) and myxoid hypocellular (C) areas, which were separated by a stromal component. The tumor cells in the solid hypercellular area were composed of densely packed round to polygonal cells, and the cells in the hypocellular area consist of uniform ovoid to spindle cells. The tumor cells were diffusely immunoreactive for vimentin (D) and partially reactive for EMA (E). Break-apart FISH assay revealed the positive split (arrow) red (22q12.1-2) and green (22q12.2) signals of EWSR1 (F).
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Histologically, the tumor appeared well defined, showing expansive rather than invasive growth, forming a multilobulated structure with alternating solid hypercellular and myxoid hypocellular areas (Fig. 2A). The hypercellular areas (Fig. 2B) displayed densely packed round to polygonal cells with pale eosinophilic cytoplasm, whereas the hypocellular myxoid areas (Fig. 2C) contained uniform ovoid to spindled cells occasionally arranged in reticular or cord-like patterns. Immunohistochemically, the tumor cells were diffusely immunoreactive for vimentin (Fig. 2D) and partially immunoreactive for EMA (Fig. 2E) and desmin (not shown) but negative for CD99 (not shown). The FISH assay (Fig. 2F) showed EWSR1 rearrangement.