Classification of Central Nervous System Tumors

The classification of childhood central nervous system (CNS) tumors is based on histology and location.[1] Tumors are classically categorized as infratentorial, supratentorial, parasellar, or spinal. Immunohistochemical analysis, cytogenetic and molecular genetic findings, and measures of mitotic activity are increasingly used in tumor diagnosis and classification, and will likely alter classification and nomenclature in the future.

Primary CNS spinal cord tumors comprise approximately 1% to 2% of all childhood CNS tumors. The classification of spinal cord tumors is based on histopathologic characteristics of the tumor and does not differ from that of primary brain tumors.[2-4]

Infratentorial (posterior fossa) tumors include the following:

1. Cerebellar astrocytomas (most commonly pilocytic, but also fibrillary and less frequently, high-grade).
2. Medulloblastomas (classic, desmoplastic/nodular, extensive nodularity, anaplastic, or large cell) and variants.
3. Ependymomas (cellular, papillary, clear cell, tanycytic, or anaplastic).
4. Brain stem gliomas (typically diffuse intrinsic pontine gliomas or diffuse intrinsic high-grade tumors that are diagnosed neuroradiographically without biopsy; focal, tectal, and exophytic cervicomedullary tumors are generally low-grade tumors).
5. Atypical teratoid/rhabdoid tumors.
6. Choroid plexus tumors (papillomas and carcinomas).
7. Rosette-forming glioneuronal tumors of the fourth ventricle.

Supratentorial tumors include the following:

1. Low-grade cerebral hemispheric astrocytomas (grade I [pilocytic] astrocytomas or grade II [diffuse] astrocytomas).
2. High-grade or malignant astrocytomas (anaplastic astrocytomas and glioblastoma [grade III or grade IV]).
3. Mixed gliomas (low- or high-grade).
4. Oligodendrogliomas (low- or high-grade).
5. Primitive neuroectodermal tumors (PNETs) (cerebral neuroblastomas, pineoblastomas, and ependymoblastomas).
6. Atypical teratoid/rhabdoid tumors.
7. Ependymomas (cellular or anaplastic).
8. Meningiomas.
9. Choroid plexus tumors (papillomas and carcinomas).
10. Tumors of the pineal region (pineocytomas, pineoblastomas, pineal parenchymal tumors of intermediate differentiation, and papillary tumors of the pineal region).
11. Neuronal and mixed neuronal glial tumors (gangliogliomas, desmoplastic infantile astrocytoma/gangliogliomas, dysembryoplastic neuroepithelial tumors, subependymal giant cell tumors, pleomorphic xanthoastrocytoma, and papillary glioneuronal tumors).
12. Metastasis (rare) from extraneural malignancies.

Parasellar tumors include the following:

1. Craniopharyngiomas.
2. Diencephalic astrocytomas (central tumors involving the chiasm, hypothalamus, and/or thalamus) that are generally low-grade (including astrocytomas, grade I [pilocytic] or grade II [diffuse]).
3. Germ cell tumors (germinomas or nongerminomatous).

Spinal cord tumors include the following:

1. Low-grade cerebral hemispheric astrocytomas (grade I [pilocytic] astrocytomas or grade II [diffuse] astrocytomas).
2. High-grade or malignant astrocytomas (anaplastic astrocytomas and glioblastoma [grade III or grade IV]).
3. Gangliogliomas.
4. Ependymomas (often myxopapillary).

1. Louis DN, Ohgaki H, Wiestler OD, et al., eds.: WHO Classification of Tumours of the Central Nervous System. 4th ed. Lyon, France: IARC Press, 2007. 
   
   
2. Constantini S, Miller DC, Allen JC, et al.: Radical excision of intramedullary spinal cord tumors: surgical morbidity and long-term follow-up evaluation in 164 children and young adults. J Neurosurg 93 (2 Suppl): 183-93, 2000.  [PUBMED Abstract]
   
   
3. Bouffet E, Pierre-Kahn A, Marchal JC, et al.: Prognostic factors in pediatric spinal cord astrocytoma. Cancer 83 (11): 2391-9, 1998.  [PUBMED Abstract]
   
   
4. Hardison HH, Packer RJ, Rorke LB, et al.: Outcome of children with primary intramedullary spinal cord tumors. Childs Nerv Syst 3 (2): 89-92, 1987.  [PUBMED Abstract]