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Childhood Astrocytomas Treatment (PDQ®): Treatment - Health Professional Information [NCI] - General Information

Table 1. World Health Organization (WHO) Histologic Grade and Corresponding Classification for Tumors of the Central Nervous System

WHO Histologic GradeGrade Classification
ILow grade
IILow grade
IIIHigh grade
IVHigh grade

In 2007, the WHO further categorized astrocytomas, oligodendroglial tumors, and mixed gliomas according to histopathologic features and biologic behavior. It was determined that the pilomyxoid variant of pilocytic astrocytoma may be a more aggressive variant and may be more likely to disseminate, and it was reclassified by the WHO as a grade II tumor (see Table 2).[1,2,4]

Table 2. Histologic Grade of Childhood Astrocytomas and Other Tumors of Glial Origin

TypeWHO Histologic Grade
Astrocytic Tumors:  
Pilocytic astrocytomaI
Pilomyxoid astrocytomaII
Pleomorphic xanthoastrocytomaII
Subependymal giant cell astrocytomaI
Diffuse astrocytoma: 
Gemistocytic astrocytomaII
Protoplasmic astrocytomaII
Fibrillary astrocytomaII
Anaplastic astrocytomaIII
GlioblastomaIV
Oligodendroglial Tumors: 
OligodendrogliomaII
Anaplastic oligodendrogliomaIII
Mixed Gliomas:  
OligoastrocytomaII
Anaplastic oligoastrocytomaIII

Childhood astrocytomas and other tumors of glial origin can occur anywhere in the CNS, although each tumor type tends to have preferential CNS locations (see Table 3).

Table 3. Childhood Astrocytomas and Other Tumors of Glial Origin and Preferential Central Nervous System (CNS) Location

Tumor TypePreferential CNS location
Pilocytic astrocytomaOptic nerve, optic chiasm/hypothalamus, thalamus and basal ganglia, cerebral hemispheres, cerebellum, brain stem, and spinal cord (rare)
Pleomorphic xanthoastrocytomaSuperficial location in cerebrum (temporal lobe preferentially)
Diffuse astrocytoma (including fibrillary)Cerebrum (frontal and temporal lobes), brain stem, spinal cord, optic nerve, optic chiasm, optic pathway, hypothalamus, and thalamus
Anaplastic astrocytoma, glioblastomaCerebrum; occasionally cerebellum, brain stem, and spinal cord
OligodendrogliomasCerebrum (frontal lobe preferentially followed by temporal, parietal, and occipital lobes), cerebellum, brain stem, and spinal cord
OligoastrocytomaCerebral hemispheres (frontal lobe preferentially followed by the temporal lobe)
Gliomatosis cerebriCerebrum with or without brain stem involvement, cerebellum, and spinal cord

More than 80% of astrocytomas located in the cerebellum are low-grade (pilocytic grade I) and often cystic; most of the remainder are diffuse grade II astrocytomas. Malignant astrocytomas in the cerebellum are rare.[1,2] The presence of certain histologic features has been used retrospectively to predict event-free survival for pilocytic astrocytomas arising in the cerebellum or other location.[5,6,7]

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