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Khang-Loon Ho

✓ There are only seven reported cases of intracranial schwannomas originating from the cranial nerves innervating the extraocular muscles. The present case, an incidental finding at autopsy, is the third case of schwannoma of the trochlear nerve and the first to illustrate the morphological relationship between this tumor and nerve. Reported cases of schwannoma of the oculomotor and trochlear nerves are summarized in a table.

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S. Ather Enam, Mark L. Rosenblum and Khang-Loon Ho

✓ A neurocytoma is a central nervous system tumor composed of small cells with features of neuronal differentiation; it typically occurs in the periventricular region, close to the septum pellucidum and the foramen of Monro. In this article, the authors report the case of a neurocytoma located in the cerebellum, which to their knowledge is the first reported case of its kind. The finding of a neurocytoma at a nonclassic location refutes the theory that this tumor has its origins in subependymal progenitor cells, unless an ectopic location of progenitor cells is invoked to explain the occurrence of a neurocytoma away from the ventricles. On the basis of this case, the authors suggest that neurocytomas should be added to the differential diagnosis of mass lesions in the supratentorial intraventricular regions as well as in the posterior fossa.

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Tom Mikkelsen, Pei-Sha Yan, Khang-Loon Ho, Mansoureh Sameni, Bonnie F. Sloane and Mark L. Rosenblum

✓ The poor prognosis of patients with malignant gliomas is at least partially due to the invasive nature of these tumors. In this study, the authors investigated the possibility that the cysteine protease cathepsin B (CB) is a participant in the process of glial tumor cell invasion. To accomplish this, an immunohistochemical analysis was made of the localization of antibodies to CB in biopsies of five specimens of normal brain, 16 astrocytomas, 33 anaplastic astrocytomas, and 33 glioblastomas multiforme.

Staining was scored according to the percentage of positive cells and the intensity of the stain, graded from 0 to 3+. Staining for CB was not seen in any of five samples of normal brain except for occasional neuronal cell bodies and microglia. Only five (31%) of 16 astrocytomas showed a small percentage of positive cells (0.01%–3%) that were stained in a light, diffuse cytoplasmic pattern (1+). Twenty-nine (87.8%) of 33 anaplastic astrocytomas showed positive light, granular staining in 2% to 40% of cells. In anaplastic astrocytoma, the staining within a tumor was heterogeneous with intensities of 1+ (17%), 1+ to 2+ (29%), or 2+ (55%). In contrast, all 33 (100%) glioblastomas were positive in 10% to 90% of cells. The staining was present in a coarse, granular pattern with an intensity of 2+ (12%) or 3+ (88%). Tumor cells infiltrating into brain adjacent to malignant gliomas stained positively in 26 cases that could be evaluated for glioblastoma multiforme; these invading cells frequently followed penetrating blood vessels as typical “secondary structures of Scherer.” Moderate to intense CB staining associated with endothelial proliferation in high-grade tumors was also observed, especially in regions of tumor infiltration into adjacent normal brain. These results provide evidence consistent with the hypothesis that CB is functionally significant in the process of tumor invasion and angiogenesis in the clinical progression of the malignant phenotype in astrocytomas.