These tumors show low cellularity, low proliferative and mitotic activity, and rarely metastasize or undergo malignant transformation. (grade 1) Pilomyxoidastrocytoma (PMA) is a recently defined variant of pediatric low-grade astrocytoma. (PMAs) have been found to have different histologic features and more aggressive than pilocyticastrocytomas. (Diffuse) The brain stem and spinal cord are the next most frequently affected sites.
Astrocytoma Astrocytoma is the most common brain tumor, accounting for more than half of all primary CNS malignancies.(Peads) Originate in glial-cells: called astrocytes. Astrocytomascome in four major subtypes: Juvenile pilocyticastrocytoma (grade 1) Fibrillary/diffuse astrocytoma (grade 2) Anaplasticastrocytoma (grade 3) Glioblastomamultiforme (grade 4) Most cases occur in the first decade of life Peak age at 5-9 years.
Astrocytoma Pilocyticastrocytomasarise throughout the neuraxis, but preferred sites optic nerve, optic chiasm / hypothalamus, thalamus and basal ganglia, cerebral hemispheres, cerebellum, and brain stem. Diffuse astrocytomasmay arise in any area of the CNS but most commonly cerebrum, particularly the frontal and temporal lobes. Anaplasticastrocytoma arises in the same locations as diffuse astrocytomas, with a preference for the cerebral hemispheres increased cellularity, marked mitotic activity, and a tendency to infiltrate through neighboring tissue.
Astrocytoma Glioblastomamultiformesubcortical white matter of the cerebral hemispheres. Combined frontotemporal location with infiltration into the adjacent cortex, basal ganglia, and contralateral hemisphere is typical. Glioblastoma most frequent brain stem in children. These tumors are highly cellular, with high proliferative and mitotic activity.
Juvenile pilocyticastrocytoma of the cerebellum (MRI). Supratentorial glioblastoma multiforme(MRI)
T2-weighted image of a diffuse intrinsic pontineglioma. Grade 2 diffuse astrocytoma
Medulloblastoma Medulloblastoma is the most common malignant brain tumor in children, accounting for 10-20% of primary CNS neoplasms and approximately 40% of all posterior fossatumors Highly invasive embryonalneuroepithelialtumor Cerebellartumor arising predominantly from the cerebellarvermis Morphologically similar tumors arising in the pineal region are termed pineoblastomas, and those arising in other CNS locations are called primitive neuroectodermaltumors (PNETs)
Medulloblastoma The tumor may spread contiguously, to the cerebellar peduncle and/or the floor of the fourth ventricle anteriorly, to the brainstem Inferiorly, to the cervical spine Superiorly, above the tentorium. It also may spread via the CSF intracranially or to the leptomeninges and spinal cord.
A cross-section of medulloblastoma (PNET) sitting in the cerebellum MRI showing a medulloblastoma of the cerebellum.
Ependymoma Ependymoma neoplasm composed of glial cells that have differentiated along ependymallines. Most common Ependymallining of the ventricles (most often the floor, roof, or lateral recesses of the fourth ventricle) but it also arises in the filumterminale and the central spinal canal. 3rd most common brain tumor in children, accounting for approximately 10% of primary CNS neoplasms Tends to invade locally, even if histological appearance is benign. Approximately 90% of tumors are intracranial, with as many as 70% occurring in the posterior fossa.
Anaplasticependymoma of the lateral ventricle in an 8-week-old girl with hydrocephalus Ependymoma of the 4th ventricle (CT-contrast) - Ventricular enlargement
Craniopharyngioma Craniopharyngiomashistologicallybenign neuroepithelial tumors that are predominately observed in children aged 5-10 years. These tumors arise from squamous cell embryologic rests found along the path of the primitive adenohypophysis and craniopharyngeal duct. Pediatric craniopharyngiomas are believed to arise from cellular remnants of the Rathke pouch, which is an embryologic structure that forms both the infundibulum and anterior lobe of the pituitary gland.
Note that the lesion is sharply demarcated and smoothly contoured. This fluid-filled mass is consistent with a typical craniopharyngioma. Image demonstrates a cystic lesion in the typical location of a craniopharyngioma.
Choroid plexus papillomas Choroid plexus papillomas may arise wherever a choroid plexus exists. In all age groups, the sites at which choroid plexus papillomas occur, in order of frequency, are the lateral ventricles (43%), fourth ventricle (39%), third ventricle (10%), and cerebellopontine angle (8%). Of all choroid plexus papillomas, 20% occur in patients younger than 1 year old, and 85% occur in those younger than 10 years old. On gross pathologic examination, choroid plexus papillomas appear as lobulated, encapsulated masses.
Shows intense heterogeneous enhancement extension into the third ventricle. Demonstrates enhancing lateral ventricular mass(CT).
A germ cell tumor/Germinoma Arises from primitive developing cells that form in the embryo and may otherwise become the reproductive system. Most commonly found in the pineal and suprasellar regions. Approximately 2 percent of all pediatric brain tumors. Half of it occur in young people (10-20 y.o)
Mass in the epiphysialarea These are typical localisations, the lesions crawl along the floor of the 3rd ventricle.