Chapter 1 - Epidemiology, Pathogenesis and Risk Factors of Brain Tumours

“Brain tumours” is the common term to define central nervous system (CNS) neoplasms, or CNS tumours.

The global incidence of all CNS tumours is unknown but higher than 45/100 000 patients a year.

The 2016 World Health Organization classification of CNS tumours is based on histopathological and molecular criteria and includes malignant, benign and borderline tumours. They are categorised as primary or secondary.

Primary CNS tumours include all primary tumours located in the CNS, the envelopes of the CNS and the beginning of the nerves localised in the skull and spine.

In the USA, the incidence rate of all primary malignant and non-malignant CNS tumours is 21.42/100 000 (7.25/100 000 for malignant and 14.17/100 000 for non-malignant tumours).

In the USA, among the various histological groups of primary CNS tumours, meningiomas account for 36%, gliomas for 28%, nerve sheath tumours for 8% and lymphomas for 2%.


Secondary CNS tumours are CNS metastases; they are all malignant. CNS metastases are single or multiple.

Metastatic tumours are the most frequent type of CNS tumour in adults. The reported incidence of metastatic CNS tumours is increasing but the exact incidence is unknown.

In general, the sources of brain metastases (in descending order) are: cancers of the lung, breast, skin (melanoma), kidney and gastrointestinal tract.

Revision Questions

  1. Do brain tumours always have the same origin?
  2. Name the two most common histological groups among primary tumours.
  3. Which brain tumours are more frequent: primary or secondary?

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Last update: 18 September 2017