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  Disease summary:

  
  
  
  
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    Primary central nervous system (CNS) tumors are a heterogeneous group of neoplasms arising from different cells of the CNS. CNS tumors may be associated with common genetic variation (sporadic tumors) and rare monogenic disorders (familial tumor syndromes).

    
    
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    Primary CNS tumors include both benign and malignant neoplasms, and in adults primarily consist of tumors of the neuroepithelial tissue and tumors of the meninges.

    
    
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    Tumors of neuroepithelial tissue account for approximately 34% of all primary brain and CNS tumors, and include in decreasing order of incidence: glioblastomas, lower-grade astrocytomas, oligodendrogliomas, ependymomas, and medulloblastomas. Neuroepithelial tumors are frequently malignant.

    
    
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    Tumors of the meninges account for approximately 36% of all primary brain and CNS tumors, and includes in decreasing order of incidence: meningiomas and hemangioblastomas. Tumors of the meninges are frequently benign.

  
  

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  Differential diagnosis:

  
  
  
  
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    Symptoms of a primary CNS tumor can overlap with those of other neoplastic and non-neoplastic conditions, including metastatic brain tumors, peripheral nervous system tumors (eg, vestibular Schwannoma, chordoma), abscess or viral infection of the brain, cerebral infarct, cerebral hemorrhage, or encephalomyelitis (eg, multiple sclerosis, acute disseminated encephalomyelitis).

  
  

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  Monogenic forms:

  
  
  
  
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    Numerous hereditary syndromes confer an increased risk for development of CNS tumors, including neurofibromatosis type 1, neurofibromatosis type 2, von Hippel-Lindau disease, tuberous sclerosis, Lynch syndrome, familial adenomatous polyposis, Li-Fraumeni syndrome, Cowden syndrome, melanoma-neural system tumor syndrome, and Gorlin syndrome (Table 41-1).

  
  

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  Family history:

  
  
  
  
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    A family history of glioma confers approximately a twofold increased risk for development of glioma. Similarly, a family history of meningioma confers 3.5-fold increased risk for development of meningioma.

  
  

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  Twin studies:

  
  
  
  
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    Twin or heritability studies have not been conducted for sporadic CNS tumors.

  
  

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  Environmental factors:

  
  
  
  
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    Ionizing radiation increases CNS tumor risk. Personal history of allergies decreases meningioma and glioma risk. Men have a 20%-60% increased risk for glioblastoma compared to women, while women have a more than two-fold increased risk for meningioma compared to men.

  
  

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  Genome-wide associations:

  
  
  
  
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    Genome-wide association studies (GWAS) have identified a single meningioma risk locus and eight independently significant glioma risk loci (Table 41-2).

  
  

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  Pharmacogenomics:

  
  
  
  
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    In tumor genomes, IDH1 or IDH2 mutation, 1p or 19q codeletion, and MGMT promoter hypermethylation are all correlated with improved prognosis and an increased response to chemotherapy in patients with glioma.

  
  

Diagnostic Criteria for CNS Tumors

While a comprehensive neurologic examination is needed, conclusive diagnosis of a CNS tumor requires some form of neuroradiologic imaging, most commonly gadolinium-enhanced magnetic resonance imaging (MRI). Determination of tumor type and histology can further be achieved:

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  A full patient workup is necessary to diagnose a primary CNS tumor and exclude the possibility that the identified lesion is a metastasis from a primary tumor at another anatomic site.

  
  
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  MRI may indicate the specific tumor type, especially in the case of meningiomas, and can further visualize the tumor and its relationship to the surrounding normal brain.

  
  
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  Accurate diagnosis of a CNS tumor requires a tissue sample for histologic study, obtained either by biopsy or open surgery. Histopathologic diagnosis of low-grade glioma using only stereotactic biopsy comes with substantial risk of inaccuracy due to sampling error.

  
  
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  A definitive diagnosis of tumor type or grade requires examination of tissue sections stained by hematoxylin and eosin.

  
  
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  Important additional information may be obtained by a trained neuropathologist through immunohistochemical staining and cytogenetic testing of tissue sections.

Clinical Characteristics

Local brain invasion, compression of adjacent regions and increased intracranial pressure in patients with a primary CNS tumor can manifest as a number of different symptoms, including:

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