Chapter 7

TUMORS OF THE CENTRAL NERVOUS SYSTEM

EPENDYMOMA AND CHOROID PLEXUS TUMORS

EPENDYMOMA


Ependymoma of the 4th ventricle

Ependymoma of the 4th ventricle. Lateral view. Reproduced with the permission of the Department of Radiology of Akron Children's Hospital.


Ependymoma of the 4th ventricle and hydrocephalus.

Ependymoma of the 4th ventricle and hydrocephalus. T2 MRI, coronal view. Reproduced with the permission of the Department of Radiology of Akron Children's Hospital.


Ependymoma of the 4th ventricle

Ependymoma arising from the floor of the 4th ventricle.

Ependymomas are predominantly tumors of children and adolescents. They arise most frequently in the fourth ventricle and cause hydrocephalus by blocking CSF flow. However, they may occur anywhere in relation to the ventricular system or central canal and are the most common primary intra-axial tumors in the spinal cord and filum terminale. Ependymomas are well demarcated from the surrounding brain and spinal cord and grow in an exophytic fashion, protruding into and out of the fourth ventricle. Spinal ependymomas are circumscribed intra-axial masses.


Ependymoma. Perivascular pseudoresette.

Ependymoma: true rosettes

Ependymoma. Tubular formations (true rosettes). Perivascular pseudorosettes are also present.


Ependymoma-EM

Ependymoma-EM.Cilia, microvilli, desmosomes.


Myxopapillary ependymoma

Myxopapillary ependymoma. Papillary formations with a mucinous (clear) core.


Myxopapillary ependymoma

Myxopapillary ependymoma. Papillary formations with a mucinous core. Alcian blue stain

Microscopically, the tumor cells resemble normal ependymal cells and are arranged in perivascular formations, tubular structures like the central canal of the spinal cord, and papillary formations. Ependymoma has distinctive ultrastructural features, including cilia, microvilli, and desmosomes. Myxopapillary ependymoma, characterized by papillary formations with a mucinous core, is a special variant, arising most commonly in the lumbosacral spinal cord and sometimes in the soft tissues of the lumbosacral region. Most ependymomas are histologically and biologically low-grade, but surgical resection of fourth-ventricle ependymomas is difficult. Some ependymomas have increased cellular density, mitoses, necrosis, and microvascular proliferation while retaining the typical ependymoma tissue pattern (anaplastic ependymoma, WHO grade III). The majority of supratentorial ependymomas in children have a characteristic molecular change, which is fusion of C11orf95 and RELA genes (RELA fusion-positive ependymomas). Clinical outcome is worse in very young patients with incomplete surgical resection, and these clinical parameters are more important for prognosis than histology.

CHOROID PLEXUS TUMORS


Choroid plexus papilloma

Choroid plexus papilloma. Benign appearance, similar to normmal choroid plexus.


Choroid plexus carcinoma

Choroid plexus carcinoma. Papillary architecture but high cellularity and atypia.

Choroid plexus tumors affect mostly children and young adults. Choroid plexus carcinoma-CPC (WHO grade III) is most common in very young children, and choroid plexus papilloma-CPP (WHO grade I) is seen in older patients. In children, CPP and CPC arise in both, lateral and fourth ventricles. In adults, CPP is more frequent in the fourth ventricle and sometimes arises in the cerebellopontine angle. CPP is seen in the Aicardi syndrome, an X-linked syndrome in females, characterized by agenesis of the corpus callosum, chorioretinal lacunae, and infantile spasms. CPC occurs in the rhabdoid tumor predisposition syndrome, caused by germline mutations of the INI1 gene. Choroid plexus tumors cause hydrocephalus and increased intracranial pressure by blocking CSF pathways and by oversecreting CSF. CPC can also seed the subarachnoid space. Both, CPP and CPC have a papillary basic structure. In CPP the papillae are covered by a single layer of benign epithelial cells, similar to normal choroid plexus. In CPC the tumor cells are multilayered, atypical, and mitotic, and the papillary structure may be effaced such that the tumor appears solid.


Updated: October, 2016

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