**2. Brain tumour types**

Brain tumours affect approximately 5–10 persons per 100,000 populations. In adults, about half of all brain neoplasms are primary tumours and the other half are metastatic. In child‐ hood, brain neoplasms account for up to 20% of all cancers. Seventy percentage of childhood brain tumours arise from the posterior cranial fossa, whereas in adults, a similar proportion arises above the tentorium [1].

Intracranial tumours may spread directly to adjacent structures, along white matter tracts, or through the cerebrospinal fluid (CSF) spaces. It is rare for brain malignancy to metastasise to other parts of the body.

The most widely accepted system for classifying brain tumours is the World Health Organisation (WHO) classification of tumours of the central nervous system (CNS), which is based on the histological characteristics of the tumour. The latest revision was published in 2007 [2].

#### **2.1. Gliomas**

Gliomas are tumours of glial cells and include astrocytomas, oligodendrogliomas and epen‐ dymomas. Unlike most neurons, glial cells retain the ability to undergo cell division in the adult CNS. Since carcinogenesis is related to the sequential accumulation of genetic aberra‐ tions through cell division, it is not surprising that gliomas are the most common primary brain malignancy and account for about half of all adult brain tumours. The WHO classifica‐ tion of CNS tumours additionally classifies gliomas into Grade I to IV depending on the degree of tumour histological differentiation (**Table 1**).



**Table 1.** WHO grading of tumours of the CNS.

#### **2.2. Brain metastases**

**2. Brain tumour types**

184 Neurooncology - Newer Developments

arises above the tentorium [1].

other parts of the body.

2007 [2].

**2.1. Gliomas**

 **Astrocytic tumours**

 **Oligoastrocytic tumours**

Subependymoma •

Brain tumours affect approximately 5–10 persons per 100,000 populations. In adults, about half of all brain neoplasms are primary tumours and the other half are metastatic. In child‐ hood, brain neoplasms account for up to 20% of all cancers. Seventy percentage of childhood brain tumours arise from the posterior cranial fossa, whereas in adults, a similar proportion

Intracranial tumours may spread directly to adjacent structures, along white matter tracts, or through the cerebrospinal fluid (CSF) spaces. It is rare for brain malignancy to metastasise to

The most widely accepted system for classifying brain tumours is the World Health Organisation (WHO) classification of tumours of the central nervous system (CNS), which is based on the histological characteristics of the tumour. The latest revision was published in

Gliomas are tumours of glial cells and include astrocytomas, oligodendrogliomas and epen‐ dymomas. Unlike most neurons, glial cells retain the ability to undergo cell division in the adult CNS. Since carcinogenesis is related to the sequential accumulation of genetic aberra‐ tions through cell division, it is not surprising that gliomas are the most common primary brain malignancy and account for about half of all adult brain tumours. The WHO classifica‐ tion of CNS tumours additionally classifies gliomas into Grade I to IV depending on the

 Subependymal giant cell astrocytoma • Central neurocytoma • Pilocytic astrocytoma • Extraventricular neurocytoma • Pilomyxoid astrocytoma • Cerebellar liponeurocytoma • Diffuse astrocytoma • Paraganglioma of the spinal cord • Pleomorphic xanthoastrocytoma • Papillary glioneuronal tumour • Anaplastic astrocytoma • Rosette-forming glioneuronal tumour of the fourth ventricle •

 **Oligodendroglial tumours** Pineal parenchymal tumour of intermediate differentiation • • Oligodendroglioma • Pineoblastoma • Anaplastic oligodendroglioma • Papillary tumour of the pineal region • •

Anaplastic oligoastrocytoma • Medulloblastoma •

**Ependymal tumours** Atypical teratoid / rhabdoid tumour •

**I II III IV I II III IV** 

Pineocytoma •

CNS primitive neuroectodermal tumour (PNET) •

degree of tumour histological differentiation (**Table 1**).

 Glioblastoma • Giant cell glioblastoma •

Gliosarcoma • **Pineal tumours**

Oligoastrocytoma • **Embryonal tumours**

Myxopapillary ependymoma • **Tumours of the cranial and paraspinal nerves**

Ependymoma • Schwannoma •

The most common primary malignancies that metastasise to the brain are carcinomas of the lung, breast and melanoma [3]. The meninges are also a frequent site of metastatic disease involvement.

The following sections on molecular imaging with PET radiotracers will focus on gliomas and intracranial metastases as the cause of the majority of morbidity and mortality in neurooncol‐ ogy.
