Tumors of the nervous system are the group of neoplasms that arise from or metastasize to brain, spinal cord, meninges, or nerves. They include a wide variety of histological types and grades of malignancy as well as genetic heterogeneity. This creates a diagnostic complexity that requires a combined approach to incorporate imaging, histopathology, and genomic methods. Treatment is based on morphologic and, increasingly, molecular data, and often involves a multidisciplinary approach with surgery, irradiation, and chemotherapy as well as targeted therapies. In spite of the recent advances in diagnosis and treatment, prognosis of the most common primary neoplasms—high-grade gliomas—remains poor.
Tumors of the nervous system define a large group of neoplasms that arise from the different cell types constituting the central nervous system (CNS; neuroepithelial tumors, pituitary tumors), its covering (meningeal tumors), the peripheral nervous system (nerve sheath tumors), lymphatic or hematopoietic cells, and developmental remnants (germ cell tumors). These primary tumors are outnumbered by nervous system metastases. Tumors are classified by location (supratentorial, infratentorial, and spinal), cell of origin (astrocytoma, oligodendroglioma, ependymoma, etc), pathological behavior (high grade, low grade), relation to neural tissue (intra-axial, extra-axial, intradural–extramedullary, intramedullary, etc), and radiological (contrast enhancing, cystic, etc). A combination of classification methods can be used in a comprehensive way of analyzing a CNS tumor and making a decision on how to manage them.
Throughout this chapter, we will be mainly using the World Health Organization (WHO) pathological classification system, which is primarily based on histopathologic appearance, cell types of origin, and growth patterns, but also with constant references to other methods to achieve this comprehensive approach. The WHO grading system by incorporating cell density, infiltrative capacity, number of mitoses, vascular proliferation, and necrosis, creates a scale from I to IV by which the degree of malignancy can be quantified and behavior and therapeutic response can be predicted.1
GENERAL TREATMENT PRINCIPLES FOR NERVOUS SYSTEM MALIGNANCIES
A 69-year-old woman presents with a generalized tonicclonic seizure on a background of significant vascular risk factors and no known epilepsy history. The patient arrives in the emergency department (ED) and is placed in a resuscitation bay. She has one further episode of seizure. An urgent EEG shows generalized suppression as would be expected postictally but also some sharp wave activity in temporal lead derivations. An urgent CT with contrast is performed, which shows a large enhancing lesion in the parieto-temporal junction. She is loaded with phenytoin while waiting for a neurology bed.
Her visibly distressed daughter approaches you at the computer. She has been told that her mother has a tumor in her head. She wants more information regarding what options are available. You explain that after her stabilization she will be transferred to a tertiary referral center with neurosurgical service where therapeutic decision will be made, but you indicate your willingness to give her some general information.