Book 4 - Self Instructional Manual for Cancer Registrars - SEER ...

MalignantTumorsGliomas are tumors of the neuroglia which comprise the non-nervous, supporting tissue of the brainderived chiefly from ectoderm. The most frequently occurring types are:Nerve Sheath Tumors• Astrocytoma arises from glial cells known as astro- (star-shaped) cytes (cells). Glial cells(neuroglia), which may be either protoplasmic or fibrous, provide the connective tissuewhich binds together the neurons of the central nervous system. This tumor generallyoccurs in the cerebrum of adults and the cerebellum of children and is the mostcommontype of glioma.• Glioblastoma (multiforme) is derived from embryonal astrocytes and is sometimes calledGrade IV astrocytoma. It is the most malignant of all brain tumors and occurs mostfrequently in adults arising in the cerebral hemispheres.• Oligodendroglioma arises from glial cells known as oligo- (small, few) dendro-(branching) glia. These supporting cells are located as satellites about the nerve cells,between nerve fibers, and along blood vessels. These tumors occur more commonly inthe cerebral hemispheres of adults.• Medulloblastoma is composed of undifferentiated neuroepithelial cells. It is one of themost frequent gliomas of childhood and tends to occur at the midline of the cerebellum;in young adults it is found more often in the lateral lobes of the cerebellum. Thesetumors have a proclivity for intercranial or intraspinal metastases.• Ependymoma arises from the ependymal cells which line the ventricles of the brain andthe central canal of the spinal cord. It is found most often in the fourth ventricleoccurring in children and young adults.• Neurilemmoma (neurinoma, schwannoma) arises from the neur- (nerve) (e)ilemma(covering) which is the thin membrane covering the peripheral nerves, also called thesheath of Schwann. These tumors are usually benign, but may occasionally occur in amalignant form. In the cranial cavity, they frequently arise at the root of the VIIIthnerve (cerebellopontine angle) and are called acoustic neuromas.• Neurofibrosarcoma is composed of interlacing bundles of anaplastic spindle-shaped cellswhich resemble those of nerve sheaths.NeuroepitheliomatousNeoplasms• Neuroblastoma is derived from embryonic nerve tissue (neuroblasts) arising primarilyin the autonomic nervous system and adrenal medulla, but not in the brain or spinalcord.• Meningiomas arise in the meninges, the membranes that envelop the brain and spinalcord: the dura mater, pia mater, and arachnoid. These are slow growing tumors andare most always benign. They are rare in children.,,04