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| Cerebellar Astrocytoma |
| Etiology •Astrocytomas of all grades have been associated with cranial therapeutic irradiation, exposure to pesticides, and N-Nitroso compounds. •Endogenous mutations caused by these agents or other causes act to produce astrocytomas. |
| Pathogenesis •Astrocytomas of any type and at any age are infiltrative tumors that act as mass lesions wherever they are found and cause symptoms related to the area which they infiltrate. •If untreated and even if treated (except in the case of pilocytic astrocytoma), astrocytomas are an important cause of death. Death is due to transtentorial herniation from the expanding mass lesion., |
| Epidemiology •Astrocytomas make up 60% of brain tumors. •There are 7-10 cases per 100,000 population discovered per year. • Grade I astrocytomas (pilocytic Astrocytomas) are seen in the cerebellum, brainstem and optic nerves of children. • Grade II astrocytomas are seen in the cerebral hemispheres of 20-40 year old individuals and high grade astrocytomas which are most malignant in their course are seen in patients in their 50's and 60's. |
| General Gross Description •Low grade astrocytomas appear as greyish white areas in the cerebral or cerebellar hemisphere that tend to "erase" normal structures and enlarge the area in which they arise. •Sometimes, they are associated with cysts. •High grade astrocytomas such as the glioblastoma multiforme are multiform in their appearance being firm to necrotic and yellow, grey , brown and/or hemorrhagic. |
| General Microscopic Description •The low grade astrocytomas have mainly oval pale nuclei with indistinct cytoplasmic borders and fibrillary processes with only mild pleomorphism. •Pilocytic astrocytomas are spindle shaped with numerous collections of reddish astrocytic fibers called Rosenthal fibers. •The higher the grade, the more cellular, the more pleomorphic and the more basophilic the tumor cell nuclei become. •In the glioblastoma very pleomorphic and basophilic nuclei are seen as are necrosis, mitotic figures and capillary endothelial proliferation. |
| Clinical Correlation • Astrocytomas act as progressive mass lesions of the brain parenchyma causing progressive loss of function in the areas invaded. •Invasion of the motor strip or tract causes hemiparesis followed be hemiplegia. •Invasion of the speech areas cause aphasia etc. •If the cerebral cortex is involved there may be seizures. In children with cerebellar lesions there is ataxia and partial obstruction of the fourth ventricle with increased intracranial pressure causing nausea, vomiting, lethargy and headache. •Cerebral lesions also lead to increased intracranial pressure by their mass effect. |
| References • Poirer J et.al. Manual of basic neuropathology. Philadelphia: Saunders, 1990, pp. 22-26. • Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 1342-1343. |
| Cerebellar Astrocytoma |
| Synopsis by: M.L. Grunnet M.D. (TX6000M94003)[404] |
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