**3. Classification of brain tumors in children**

**2. Epidemiology of brain tumors in children**

common in boys [2, 5].

108 Brain Tumors - An Update

**Figure 1.** Localization of CNS tumors in pediatric population [5].

The incidence of pediatric CNS tumors varies worldwide with an average of 4 cases per 100,000 children with the highest occurrence is in the United States [3]. By age groups, the highest incidence is in adolescents (15–19 years, 6.38/100,000), followed by a group of children under 1 year (6.2/100,000). Subsequently, it is slightly declining, with 5.5/100,000 children aged between 1 and 4 years; in 5–14 years, the incidence is 5.1/100,000 [2, 5]. About 25–30% are in supratentorial localization, followed by the cerebellum (15–20%), the brain stem (10–12%), the pituitary and suprasellar region (10–15%), cranial nerves (6–7%), brain ventricles (5–6.4%), spinal cord (4.3–4.6%) and 2.6–2.9% are tumors of meninges [2, 6], as shown in **Figure 1**. Also a typical localization and histological type occur in certain age group. By 1 year of age, tumors most often occur at multiple locations in the brain and in ventricles. At the age of 1–4 years, the most common site is the cerebellum, cerebral hemispheres and brain stem. In the age range from 5 to 9 years, tumors occur frequently in the cerebellum, brain stem and cerebral hemispheres. At the age from birth to 9 years, the most common tumors are gliomas and embryonal tumors (up to 1 year is the most common embryonic atypical teratoma/rhabdoid tumor (AT/RT), in the older children it is medulloblastoma (MB)). In 10–14 year age group, the most typical site is cerebral hemisphere and most frequently occurring are gliomas, tumors of the pituitary region and embryonal tumors. Adolescents (aged 15–19 years) most often have pituitary tumors, then astrocytomas and neoplastic tumors, but the incidence of meningiomas also increases. Typical localizations in this age group are the pituitary and suprasellar regions, followed by cerebral hemispheres and cerebellum. In general, brain tumors are more

There are many risk factors for brain tumor development, but to date only some hereditary syndromes (type 1 and 2 neurofibromatosis, tuberous sclerosis, Li-Fraumeni syndrome, Gorlin syndrome, Turcot syndrome, Cowden syndrome, Rubinstein-Taybi syndrome and hereditary retinoblastoma) and ionizing radiation have been verified. Other possible risk factors include: a personal history of previous cancer treatment, a family history of the CNS tumor, the parent age at the time of conception, the later contact of the child with common childhood infectious The new WHO classification of CNS tumors from 2016 for the first time uses molecular genetic characteristics for tumor classification in some cases. In this new edition, some new tumor entities appeared, some have been merged while others were excluded. Changes involving childhood tumors include: inclusion of epithelial glioblastoma, removal of the term brain gliomatosis, reclassification of the diffuse intrinsic pontine glioma to diffuse midline glioma, *H3 K27–*mutant, inclusion of the ependymoma, *RELA* fusion–positive as a separate unit and inclusion of the diffuse leptomeningeal glioneuronal tumor. The change also affected the classification of medulloblastomas, where genetically defined classification was added. The term primitive neuroectodermal tumors (CNS PNET) was eliminated while an embryonal tumor with multilayered rosettes, *C19MC*–altered was included [12].

Childhood brain tumors are also classified according to their localization into: infratentorial, supratentorial tumors and tumors of parasellar region. Most frequently observed histological types of pediatric CNS tumors are shown in **Figure 2**.

**Infratentorial** localization is typical for cerebellar astrocytoma (pilocytic astrocytoma – PA, but also diffuse less frequently anaplastic astrocytoma and glioblastoma), medulloblastomas, ependymomas, brain stem gliomas (most commonly diffuse midline glioma, *H3 K27–* mutant, PA), AT/RT and choroid plexus tumors.

**Supratentorial** localization are common: low-grade glioma—LGG (PA, diffuse astrocytoma, oligodendroglioma, mixed oligoastrocytoma, subependymal giant cell astrocytoma— SEGA, pleomorphic xanthoastrocytoma—PXA), high-grade glioma—HGG (anaplastic astrocytoma, anaplastic oligodendroglioma and glioblastoma), neuronal and mixed neuronal-glial

**Figure 2.** Most frequent histological types of CNS tumors in children [5].

tumors (ganglioglioma—GG, desmoplastic infantile astrocytoma—DIA, ganglioglioma— DIGG, dysembryoplastic neuroepithelial tumor—DNET and papillary glioneuronal tumor), embryonal tumors (embryonal tumor with multilayered rosettes, *C19MC*-altered—ETMR, medulloepithelioma, CNS neuroblastoma, CNS ganglioneuroblastoma, CNS embryonal tumor and CNS embryonal tumor with rhabdoid features), AT/RT, ependymomas, meningiomas, choroid plexus tumors, pineal tumors (pineocytomas, pineal parenchymal tumor of intermediate differentiation and papillary tumors of the pineal region) and rarely metastases of extra-neural malignant tumors.

Preoperatively, the navigational MRI is performed for the needs of intraoperative navigation. Among the disadvantages of MRI is relatively longer duration, which in smaller children requires general anesthesia. However, a huge advantage is the absence of radiation [13].

Primary Brain Tumors in Childhood

111

http://dx.doi.org/10.5772/intechopen.74510

**Computer tomography (CT)** is mostly used for the display of bones and their lesions, which do not appear in detail in MRI. Another indication may be **CT-angiography.** Due to the high dose of radiation; however, CT is reserved for cases of sudden changes in the neurological

**Positron emission tomography (PET)** uses radioactive fluorodeoxyglucose for visualization of tumor tissue that is metabolically more active. The radioactive load is very low and is excluded in 1 day. It can be used preoperatively for diagnostics as well as for postoperative distinguishing between residues, recurrences and postoperative changes in unclear cases [14]. **Angiography** (mostly DSA) uses vessel imaging after contrast agent administration to assess tumor vascular supply. It is also associated with radiation and though is currently replaced by MR- or CT-angiography. However, it remains reserved for preoperative embolization of

Specimen of CSF obtained from **lumbar puncture** is used for cytological examination to detect the presence of tumor cells that occur in CSF in tumor dissemination or in leukemia tumors. It is also used to detect the presence of tumor markers, in particular bHCG and AFP in germ cell tumors. It also serves to verify the presence of infection, especially in the postoperative

**Biopsy** of brain tumor is essential for definitive diagnosis. In most cases, tissue sample is obtained during surgery. However, there are also cases of inoperable tumors according to their localization or extent. If a tumor resection cannot be performed, a stereotactic biopsy can be useful. In some cases, however, the biopsy is too risky, and therefore the diagnosis is

Also **other examinations** could be useful, such as: EEG, evoked potentials, evaluation of neurocognitive functions, ophthalmological examination (papilledema of optic nerve and perim-

Treatment consists of surgical intervention, followed by oncological and symptomatic treat-

**Surgical treatment** is the basis of treatment and, in some tumors, it is the only sufficient form of therapy. Also histologically, benign tumors can be a surgical challenge by their localization. An essential part of brain tumor surgery is the use of microscope and micro instruments. Nowadays, it belongs to the usual equipment of surgical department, as well as ultrasonic aspirator, **navigation systems,** intraoperative sonography and possibility of realization of electrophysiological monitoring. **Electrophysiological monitoring** requires appropriate instrumentation and personnel equipment that enhances the safety of the operation to the

eter), evaluation of hearing disorder and hormone levels and function [13].

condition when rapid imaging is necessary.

the tumor, which is carried out by DSA [13].

determined only by MRI (e.g., diffuse pontine gliomas).

**6. Treatment of brain tumors**

ment and requires multidisciplinary approach.

period [13].

Tumors occurring in **parasellar** region usually are: craniopharyngiomas, adenomas, LGG astrocytomas (tumors of central regions, chiasma, hypothalamus, thalamus, PA or diffuse astrocytomas) as well as germ cell tumors.
