EPENDYMOBLASTOMA-CHILD

Childhood ependymoblastoma falls under the general category of primitive neuroectodermal tumors (PNETs) of the central nervous system. A total of about 1,200 to 1,500 children per year in the United States develop new brain tumors of all types. Worldwide, over 40,000 children are so diagnosed each year.

The causes of pediatric brain tumors are largely unknown. Certain things however, are known: exposure to radiation in the treatment for acute lymphocytic leukemia (ALL) produces an increased risk of developing brain tumors. The chemotherapy agents known as nitrosureas (nitrogen mustards) are also associated with an increased risk of later development of astrocytoma. Various familial and genetic tendencies also exist, such as basal nevus syndrome (Gorlin syndrome) and ataxia telangiectasia, but these are extremely rare. There has also been speculation about maternal exposure to carcinogens from various sources, including drinking water, during pregnancy.

The terminology surrounding primitive neuroectodermal tumors (PNET) is complex. PNET refers to a group of brain and central nervous system (CNS) tumors that originate in embryonal tissue. A group of related tumors that occurs outside the nervous system - that is, peripherally rather than centrally - is known, confusingly, as PPNET (peripheral primitive neuroectodermal tumors), but these tumors are an entirely separate entity.

PNET is overwhelmingly a disease of childhood and young adulthood, although it is also possible for mature adults to develop PNET.

PNET is classified loosely into two groups, supratentorial and infratentorial, according to whereabouts in the brain the tumor occurs. Ependymoblastoma is a supratentorial PNET, or SPNET.

About half of all brain tumors in children are "infratentorial." Three quarters of these are located in the cerebellum or fourth ventricle. Some of the common infratentorial tumors include:

• medulloblastoma
• cerebellar astrocytoma
• ependymoma
• brain stem glioma

There are close similarities between the commonest kind of PNET, medulloblastoma, and ependymoblastoma. The term PNET was introduced to encompass both medulloblastoma and other tumors that have a similar appearance under the microscope and similar clinical features, includxing ependymoblastoma, pineoblastoma, cerebral neuroblastoma and multidifferentiated supratentorial PNET.