Brain Pathology Case of the Month - October 2008

Contributed by Fang-Yi Lee, MD1, Yee-Jee Jan, MD1, 3, Mei-Chin Wen, MD1, 3, Mu-Chun Li, MD1,
    John Wang, MD, PhD1, 3, Chen Wen-Hsien, MD2
    1 Departments of Pathology, Taichung Veterans General Hospital
    2 Department of Radiology, Taichung Veterans General Hospital
    3 College of Biomedicine and Nursing HungKuang University, Taichung, Taiwan, R.O.C.


A 32-year-old man was admitted to the neurosurgery department due to progressive dizziness and weakness of the feet for a month. An MRI revealed a well-demarcated mass measuring 60x35x25 mm, obstructing the fourth ventricle with dilatation of the lateral ventricles, third ventricle and the aqueduct. The lesion showed contrast enhancement with heterogeneous low signal intensity on T1WI (Figure 1) and mixed heterogeneous low and iso-signal intensity on T2WI (Figure 2). Several foci of cystic change were noted. A gross total resection was performed.


Microscopically, the tumor was composed of pleomorphic cells with eosinophilic cytoplasm, irregular nuclear contours, and small nucleoli. In addition, there were large areas with cells that showed a signet-ring appearance, with large vacuoles in their cytoplasm and the nuclei pushed to the periphery of the cell membrane, assuming a crescent shape (Figures 3 and 4). Both types of tumor cells exhibited a perivascular arrangement and some of them even had long fibrillary cytoplasmic processes condensed about the stromal vessel in a fashion similar to the perivascular pseudorosette of a cellular ependymoma (Figure 5). Eosinophilic granular bodies were frequent, but Rosenthal fibers were absent (Figure 6). Microvascular proliferation, necrosis, and mitotic figures were not identified.

Both types of tumor cells showed strong positive staining with GFAP (Figure 7) and S-100 protein, being diffuse in the cytoplasm of the eosinophilic cells and in the rim of the signet-ring cells. Immunostains for EMA, synaptophysin, and neurofilament were negative. The Ki-67/MIB-1 labeling index was less than 10%.

Ultrastructurally, the neoplastic cells were elongated in shape and had a peripheral, deeply indented nucleus. The cytoplasm was filled with abundant intermediate filaments (Figure 8). However, in the signet-ring cells, large lipid droplets are observed within the cytoplasm (Figure 9) as well as few condensed intermediate filaments in the periphery. All of the tumor cells were surrounded by a continuous basal lamina. Neither dense core granules nor synaptic structures were found. Ependymal features such as microvilli, cilia or intercellular junctions were not identified.


International Society of Neuropathology