The classification of brain tumors is based on both histopathologic 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. Studies have suggested that the tumor cells of medulloblastomas and supratentorial primitive neuroectodermal tumors have different molecular genetic aberrations.[1,2] This group also includes some tumors formerly called central neuroblastomas. 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. The World Health Organization 2000 classification of brain tumors maintains the term medulloblastoma for posterior fossa undifferentiated tumors.[3] 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 evolving; 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. Kleihues P, Cavenee WK, eds.: Pathology and Genetics of Tumours of the Nervous System. Lyon, France: International Agency for Research on Cancer, 2000.