The classification of brain tumors is based on both histopathological characteristics and location in the brain. Undifferentiated neuroectodermal tumors of the cerebellum have historically been referred to as medulloblastomas, while tumors of identical histology in the pineal region are diagnosed as pineoblastomas, and cortical lesions have been called central neuroblastomas or cortical primitive neuroectodermal tumors. There are different molecular genetic aberrations in the tumor cells of medulloblastomas and supratentorial primitive neuroectodermal tumors.[1-3] The nomenclature of pediatric brain tumors is controversial and potentially confusing. Some pathologists advocate abandoning the traditional morphologically based classifications such as medulloblastoma in favor of a terminology that relies more extensively on the phenotypic characteristics of the tumor. In such a system, medulloblastoma is referred to as primitive neuroectodermal tumor and then subdivided on the basis of cellular differentiation.[4-7] The most recent World Health Organization classification of brain tumors maintains the term medulloblastoma for posterior fossa undifferentiated tumors.[7,8] It also maintains separate categories for cerebral primitive neuroectodermal tumors and for pineal small round cell tumors (pineoblastomas). The pathologic classification of pediatric brain tumors is a specialized area that is undergoing evolution; review of the diagnostic tissue by a neuropathologist who has particular expertise in this area is strongly recommended.

References

1. Russo C, Pellarin M, Tingby O, et al.: Comparative genomic hybridization in patients with supratentorial and infratentorial primitive neuroectodermal tumors. Cancer 86 (2): 331-9, 1999.  [PUBMED Abstract]
   
   
2. Nicholson JC, Ross FM, Kohler JA, et al.: Comparative genomic hybridization and histological variation in primitive neuroectodermal tumours. Br J Cancer 80 (9): 1322-31, 1999.  [PUBMED Abstract]
   
   
3. Pomeroy SL, Tamayo P, Gaasenbeek M, et al.: Prediction of central nervous system embryonal tumour outcome based on gene expression. Nature 415 (6870): 436-42, 2002.  [PUBMED Abstract]
   
   
4. Rorke LB: The cerebellar medulloblastoma and its relationship to primitive neuroectodermal tumors. J Neuropathol Exp Neurol 42 (1): 1-15, 1983.  [PUBMED Abstract]
   
   
5. Gilles FH: Classifications of childhood brain tumors. Cancer 56 (7 Suppl): 1850-7, 1985.  [PUBMED Abstract]
   
   
6. Dehner LP: Peripheral and central primitive neuroectodermal tumors. A nosologic concept seeking a consensus. Arch Pathol Lab Med 110 (11): 997-1005, 1986.  [PUBMED Abstract]
   
   
7. Kleihues P, Cavenee WK, eds.: Pathology and Genetics of Tumours of the Nervous System. Lyon, France: International Agency for Research on Cancer, 2000. 
   
   
8. Burger PC, Scheithauer BW: Tumors of the Central Nervous System. Washington, DC: Armed Forces Institute of Pathology,1994. 
   
   

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