The classification of brain tumors is based on both histopathologic characteristics and location in the brain. More than 80% of all childhood cerebellar gliomas will be pilocytic astrocytomas, which are also considered to be grade 1 astrocytomas. Most of the remainder will be diffuse or fibrillary astrocytomas. Malignant gliomas are rare.[1] 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.

These generally low-grade, often cystic astrocytic tumors are localized to the cerebellum. Except for malignant gliomas, contiguous spread or metastasis outside that region is extremely rare. The presence of certain histologic features has been used retrospectively to stratify cerebellar astrocytomas into two distinct groups: pilocytic or Gilles type A tumors and diffuse or Gilles type B tumors; the latter tumors have a poor prognosis.[2] Expert neuropathologic review is important.

References

1. Kleihues P, Cavenee WK, eds.: Pathology and Genetics of Tumours of the Nervous System. Lyon, France: International Agency for Research on Cancer, 2000. 
   
   
2. Gilles FH, Sobel EL, Tavaré CJ, et al.: Age-related changes in diagnoses, histological features, and survival in children with brain tumors: 1930-1979. The Childhood Brain Tumor Consortium. Neurosurgery 37 (6): 1056-68, 1995.  [PUBMED Abstract]