EPIDEMIOLOGY OF PEDIATRIC TUMORS OF THE NERVOUS SYSTEM

Tumors of the nervous system are the second commonest type of neoplasia of childhood. The major flaw of epidemiological studies based on population-based or institutional registries concerns the fact that different classification schemes may have been adopted by the several institutions from which the data are taken. In several reports dealing with this issue, the failure may arise from different concepts regarding medulloblastomas and astrocytomas, which are the most frequent neuropediatric tumors. In a number of reports, medulloblastomas and primitive neuroectodermal tumors (PNETs) are lumped together, being considered as the same type of tumors. Astrocytic tumors are frequently considered a unique neoplasm with different degrees of malignity. Actually, these tumors are a heterogeneous group of neoplasms which constitute distinct clinicopathological entities that must be individualized. With these concerns in mind, we realized a revision of our pediatric tumors of the nervous system which were classified according the WHO 2000 classification which is currently adopted in most neuropathological laboratories. We think that with this procedure our data reflect the real epidemiological status of pediatric brain tumors. In summary, our results taken from 1325 consecutive cases studied from 1974 and 2005 in children aged between 0 to 21 years, show that 1)males are more affected than females (54%/46%); 2) according to the topography, 60% were supratentorial, 30%, infratentorial, and 10% spinal; 3) ependymomas and schwanomas were the most frequent spinal tumors; 4) in the cerebral compartment pilocytic astrocytomas were the single most frequent tumor (17%) followed by diffuse astrocytomas (all grades=12%), medulloblastomas (10%), and craniopharyngeomas (9%); 5) in the posterior fossa, medulloblastomas and pilocytic astrocytomas were evenly distributed but the former is more frequent in the first two years; 6) Astrocytomas grade III and IV were slightly more frequent than grade II; 7) the frequency of neuronal and mixed tumors is increasing due to the development of surgery of epilepsy.