Ependymal Tumors

Ependymoma (Grade 1-3)

This tumor arises from the ependymal lining of the ventricular wall and either projects into the ventricular lumen or invades the parenchyma. It occurs from infancy to old age but predominates in children and adolescents. In children, it is more common in the fourth ventricle, accounting for 6% to 12% of intracranial childhood

figure 11.18

Oligodendroglioma. A 47-year-old man presented with a 2-month history of left-sided partial sensory seizures. Six months earlier, he experienced a short episode of left-sided weakness and loss of consciousness followed by confusion. A. Axial T2-weighted MRI shows a large inhomogeneous hyperintense right temporoparietal tumor extending into the basal ganglia. B. The partially resected tumor is composed of oligodendrocytes with round and oval nuclei and clear (halo) cytoplasm (fried egg appearance) (HE).

figure 11.18

Oligodendroglioma. A 47-year-old man presented with a 2-month history of left-sided partial sensory seizures. Six months earlier, he experienced a short episode of left-sided weakness and loss of consciousness followed by confusion. A. Axial T2-weighted MRI shows a large inhomogeneous hyperintense right temporoparietal tumor extending into the basal ganglia. B. The partially resected tumor is composed of oligodendrocytes with round and oval nuclei and clear (halo) cytoplasm (fried egg appearance) (HE).

figure 11.19

Oligodendroglioma showing (A) great uniformity of the tumor cells, (B) dense calcifications in the cerebral cortex, and (C) microgemistocytic components (HE).

figure 11.19

Oligodendroglioma showing (A) great uniformity of the tumor cells, (B) dense calcifications in the cerebral cortex, and (C) microgemistocytic components (HE).

tumors. It occurs in the cerebral hemispheres at any age, accounting for 5% to 6% of gliomas in all age groups.

Grossly, the tumor is fairly well demarcated and moderately firm; the cut surface is homogeneously gray and slightly granular (Fig. 11.20). Histologically, the tumor consists of medium-sized neoplastic ependymal glia with oval or round nuclei surrounded by a moderate amount of cytoplasm. Some cells have a columnar shape. The cells may form pseudorosettes around blood vessels, true rosettes lining small lumens, or small nests in a fibrillary matrix (Fig. 11.21). Rarely, the tumor contains hemorrhages, calcifications, and bony metaplasia. Genetic alteration includes loss of chromosome 22q, suggesting the presence of a tumor suppressor gene on that chromosome.

Subependymoma refers to a small nodule in the ventricular wall, usually benign and slowly growing.

figure 1 1.20

Ependymoma of the fourth ventricle in a 54-year-old man. He died following a 16-year clinical course. A. A circumscribed cherry-sized, firm, lobulated tumor fills the lumen of the fourth ventricle. B. Macrosection of the tumor at pontine level (cresyl violet).

Histologically, nests of neoplastic ependymal cells are dispersed in a fibrillary matrix (Fig. 11.22).

Choroid Plexus Papilloma (Grade 1) This benign tumor derives from the epithelial cells of the choroid plexus, and accounts for 0.5% of all intracranial tumors. It is more common in infants and children, and seldom is congenital. In children and adolescents, it has a predilection for the lateral ventricles; in adults, the fourth ventricle. Seldom, it occurs in the cerebellopontine angle. The detection of elements of the oncogenic papovavirus SV40 in some choroid plexus papillomas and carcinomas raises the possibility of the role of the virus in tumor pathogenesis.

Grossly, it is circumscribed and moderately firm, and the cut surface has a cauliflower- like appearance. When large enough, it occludes the ventricle, causing

figure 11.21

Ependymoma. A. Cuboidal ependymal cells fill the lumen of the lateral ventricle. The cells are uniform in appearance and are arranged in sheets or show no particular pattern (cresyl-violet). B. Papillary pattern (HE). C. Perivascular pseudorosettes. Some cells express GFAP (immunostain).

m figure 11.21

Ependymoma. A. Cuboidal ependymal cells fill the lumen of the lateral ventricle. The cells are uniform in appearance and are arranged in sheets or show no particular pattern (cresyl-violet). B. Papillary pattern (HE). C. Perivascular pseudorosettes. Some cells express GFAP (immunostain).

figure 1 1.22

Subependymoma. A. A small tumorous nodule is attached to the wall of the lateral ventricle, incidental autopsy finding (HE) B. Nests of tumor cells are situated in a fibrillary matrix (HE stain).

hydrocephalus and raised ICP. Histologically, the tumor resembles a normal choroid plexus, but is more cellular, with cuboidal and columnar epithelial cells resting on a fine fibrovascular stroma. Hemorrhages and calcifications are common (see Fig. 11.23).

Choroid plexus carcinoma (grade 3), a malignant variant, shows cellular pleomorphism, mitoses, and necrosis. It is prone to invade adjacent structures and to disseminate along the CSF pathways (see Fig. 11.24).

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