PMC3994688_01
Preoperative (a) axial and (b) sagittal T1-weighted contrast enhanced magnetic resonance imaging demonstrating a 2.5 x 3.7 x 2.5 cm heterogeneously enhancing cystic mass centered within the cerebellar vermis causing marked mass effect on the fourth ventricle. Preoperative (c) coronal and (d) axial T1-weighted contrast enhanced magnetic resonance imaging demonstrating an 8 x 6 x 4 mm satellite lesion within the right superior cerebellar peduncle
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F1
A magnetic resonance imaging (MRI) of the brain revealed a 2.5 x 3.7 x 2.5 cm heterogeneously enhancing cystic mass centered within the cerebellar vermis with mass effect on the fourth ventricle and mild ventriculomegaly [Figure 1a and b] as well as an 8 x 6 x 4 mm satellite lesion within the right superior cerebellar peduncle [Figure 1c and d].
Specimen resected at surgery demonstrating: (a) piloid tumor cells within a myxoid background (hematoxylin and eosin, x10); (b) tumor cells with a perivascular orientation, lack of Rosenthal fibers identified (arrow) (hematoxylin and eosin, x20); (c) nonreactive blood vessels surrounded by reactive tumor cells (glial fibrillary acidic protein (GFAP), x20); (d) tumor cells with low proliferative index (Ki-67 (MIB-1), x10)
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F2
Permanent section of the lesion demonstrated a glial neoplasm composed of astrocytes with elongated, bipolar cytoplasmic processes, forming fascicles and focally, loose perivascular patterns, dispersed within an abundant myxoid background [Figure 2a and b]. They were strongly immunoreactive for GFAP and WT-1 with a MIB-1 labeling index of greater than 5% [Figure 2c and d].