LABORATORY DATA
Noncontributory.

ANCILLARY STUDIES
Computed tomography (CT) of the head revealed a right parietal-occipital mass lesion composed of a large radiolucent cystic area underlying a superficial solid area which showed contrast enhancement (Figure 1). T1-weighted magnetic resonance imaging (MRI) showed findings similar to CT imaging, with a large hypodense cystic mass with an isodense peripheral solid component which enhanced with gadolinium (Figure 2). Both CT and MRI imaging showed cerebral edema surrounding the lesion without shift of the midline structures.

Figure 1:	Figure 2:

GROSS PATHOLOGY
After administration of Decadron to reduce the cerebral edema, the patient underwent craniotomy. At surgery, a poorly vascularized tumor was identified, which was inseparable from the overlying dura and surrounded by a thin fibrous pseudocapsule. Adjacent to the undersurface of the solid portion of the mass was a large well-circumscribed, multiloculated cyst that collapsed spontaneously. The tissue resected from the parietal-occipital lobe was received in surgical pathology as multiple irregular fragments of variable sizes measuring, in aggregate, 13.6 cm in maximum dimension. Individual fragments were predominantly white with a rubbery consistency. Several fragments also showed an outer tan-gray fibrotic area measuring up to 0.4 cm in thickness. A small portion of the tissue contained focal areas with smooth contours consistent with cyst wall components. There was no gross evidence of hemorrhage or necrosis.

MICROSCOPIC PATHOLOGY
The predominant microscopic feature of the tumor was prominent desmoplasia with a combination of astroglial, neuronal, and fibroblastic elements (Figures 3 and 4). Masson's trichrome revealed wavy collagenous fibrils investing the cellular components (Figure 5). Overall, astroglial cells were the most conspicuous cellular component especially in regions with the most abundant desmoplasia. These astroglial cells were moderately pleomorphic, ranging from elongated, spindle cells to polygonal forms, all of which were readily identified by glial fibrillary acid protein (GFAP) immunostaining (Figure 6). Neuronal elements were sparse and heterogeneous, predominantly consisting of polygonal cells with round, vesicular nuclei and prominent nucleoli. Rare atypical ganglion-like forms were also identified. Synaptophysin and neuron specific enolase (NSE) facilitated identification of the neuronal elements (Figures 7 and 8). Aggregates of poorly differentiated neuroectodermal cells with small round deeply basophilic nuclei and minimal surrounding perikarya were found scattered throughout the tumor in small aggregates.

Figure 3:	Figure 4:	Figure 5:
Figure 6:	Figure 7:	Figure 8:

A sharp demarcation between the tumor and the cortical surface was found in several tissue sections although the Virchow-Robin spaces in underlying areas were often filled with tumor cells. Mitotic activity was scant, and rare proliferating cells showed immunoreactivity for Ki-67 with a labeling index <1%. Positive staining for P53 was present in a significant minority ( 35%) of astroglial cells.

Ultrastructurally the predominant cell types identified were astroglial and fibroblastic with only rare neuronal cells identified (Figure 9). Astroglial cells contained numerous intermediate filaments, a moderate number of mitochondria and endoplasmic reticulum, and often some degree of pericellular basal lamina formation (Figure 10). Neuronal cells showed small stacks of rough endoplasmic reticulum and microtubule containing processes containing both vesicles and neurosecretory granules. Spindle-shaped fibroblast cells were characterized by prominent Golgi complexes, abundant ribosomes, and numerous bundles of intercellular collagen fibers.

Figure 9:	Figure 10: