Low-Grade Cerebral Astrocytoma
High-Grade Cerebral Astrocytoma

Low-Grade Cerebral Astrocytoma

Low-grade cerebral astrocytomas (grade I [pilocytic] and grade II) have a relatively favorable prognosis, particularly if complete excision is possible.[1,2] In the World Health Organization brain tumor classification schema, all grade 1 tumors are pilocytic astrocytomas. The pilomyxoid variant of pilocytic astrocytoma may be a more aggressive variant and may be more likely to disseminate.[3] There is no generally recognized staging system. Tumor spread, when it occurs, is usually by contiguous extension; dissemination to other central nervous system sites may rarely occur. Although metastasis is unlikely, tumors may be of multifocal origin, especially when associated with neurofibromatosis type 1 (NF-1). Low-grade astrocytomas have a predilection for certain anatomic locations in children, including the cerebellum, diencephalon (i.e., chiasm, hypothalamus, and thalamus), and brainstem.

Patients with NF-1 constitute a special group of patients with low-grade gliomas. In general, treatment is not required for incidental tumors found with surveillance scans. Symptomatic lesions or those that have radiographically progressed may require treatment.[4]

High-grade or malignant astrocytoma (anaplastic astrocytoma [grade III] and glioblastoma multiforme [grade IV]) may occur anywhere above the tentorium. Malignant astrocytoma is often locally invasive and extensive.[1,2] Spread via the subarachnoid space may occur. Metastasis outside of the central nervous system has been reported but is extremely infrequent until after multiple local relapses. There is no generally recognized staging system. Biologic markers, such as p53 overexpression and mutation status, may be useful predictors of outcome in patients with malignant gliomas.[5] Although malignant astrocytoma carries a generally poor prognosis in younger patients, those with anaplastic astrocytoma and those in whom a gross total resection is possible may fare better.[6]

References

1. Pollack IF: Brain tumors in children. N Engl J Med 331 (22): 1500-7, 1994.  [PUBMED Abstract]
   
   
2. Deutsch M, ed.: Management of Childhood Brain Tumors. Boston: Kluwer Academic Publishers, 1990. 
   
   
3. Komotar RJ, Burger PC, Carson BS, et al.: Pilocytic and pilomyxoid hypothalamic/chiasmatic astrocytomas. Neurosurgery 54 (1): 72-9; discussion 79-80, 2004.  [PUBMED Abstract]
   
   
4. Molloy PT, Bilaniuk LT, Vaughan SN, et al.: Brainstem tumors in patients with neurofibromatosis type 1: a distinct clinical entity. Neurology 45 (10): 1897-902, 1995.  [PUBMED Abstract]
   
   
5. Pollack IF, Finkelstein SD, Woods J, et al.: Expression of p53 and prognosis in children with malignant gliomas. N Engl J Med 346 (6): 420-7, 2002.  [PUBMED Abstract]
   
   
6. Finlay JL, Boyett JM, Yates AJ, et al.: Randomized phase III trial in childhood high-grade astrocytoma comparing vincristine, lomustine, and prednisone with the eight-drugs-in-1-day regimen. Childrens Cancer Group. J Clin Oncol 13 (1): 112-23, 1995.  [PUBMED Abstract]
   
   

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