Chapter 1 - Epidemiology, Pathogenesis and Risk Factors of Brain Tumours
Epidemiological data on primary CNS tumours come from registries and population studies. But registration guidelines and population vary among registries and countries, so results from the literature should be analysed according to these differences.
Primary CNS tumours are divided into major histological groups.
More than 90% of neuroepithelial tissue tumours are malignant, and more than 90% of meningeal tumours are non-malignant.
In adults, the male/female ratio for diffuse gliomas is approximately 1.5. Among these, glioblastoma (Grade 4 glioma) is the most frequent. The median age at diagnosis is 64 years.
Diffuse Grade 2 gliomas (DGIIGs, often named diffuse low-grade gliomas) and diffuse Grade 3 gliomas (DGIIIGs, often named anaplastic gliomas) account for approximately 30% of all gliomas.
Median age at diagnosis is 43 years for DGIIG and 56 years for DGIIIG.
In the USA, the incidence rate of paediatric (<15 years old) primary CNS tumours is 5.3 cases per 100 000. These tumours are the most common paediatric solid tumours.
Paediatric gliomas include pilocytic astrocytomas (Grade 1 glioma, 33%), Grade 3 and 4 gliomas (21%), ependymal tumours (10%) and all other gliomas (36%).
All embryonal tumours are malignant. Medulloblastoma is the most important subgroup of embryonal tumours (62%).
Revision Questions
- Why can epidemiological data differ from one country to the next?
- Are diffuse gliomas more frequent in women or men?
- What is the most frequent grade of glioma in children?
