Gliomas are the most common brain tumors, which begin in the glial (supportive) tissue. There are different types of gliomas, including astrocytomas, brain stem gliomas, ependymomas, and oligodendrogliomas.1
An astrocytoma develops from astrocytes that support nerve cells and may grow in the brain or spinal cord.1
Grade I: Pilocytic astrocytoma (Juvenile Pilocytic Astrocytoma)
Pilocytic astrocytoma is a slow growing, relatively well-defined tumor that develops in the cerebrum, optic nerve pathways, brain stem, and cerebellum. It occurs most often in children and teens.2
Grade I: Subependymal giant cell astrocytoma
Subependymal giant cell astrocytoma is a benign, slow growing tumor that develops in the wall of the lateral ventricles.2
Grade II: Low-grade astrocytoma (pleomorphic xanthoastrocytoma)
Pleomorphic xanthoastrocytoma has a relatively favorable prognosis. It is commonly found in the cerebral hemispheres and may involve the meninges. It occurs most often in children and young adults.2
Grade II: Low-grade astrocytoma (diffuse astrocytoma)
Diffuse astrocytoma is characterized by high cellular differentiation and slow growth. It has a tendency to progress to anaplastic astrocytoma (grade III) and glioblastoma (grade IV).4
Grade III: Anaplastic astrocytoma
Anaplastic astrocytoma primarily affects adults and grows faster and more aggressively than a grade II astrocytoma. Histologically, it is characterized by nuclear atypia, increased cellularity, and increased proliferative activity.2,4
Grade IV: Giant cell glioblastoma
Giant cell glioblastoma, often located in the temporal and parietal lobes, is a rare tumor type with multinucleated giant cells and an abundant stromal reticulin network.2
Grade IV: Glioblastoma multiforme (GBM)
GBM, the most common, deadliest brain tumor in adults, occurs in the cerebral hemispheres or other parts of the brain, brainstem, or spinal cord. Characteristics include nuclear atypia, cellular pleomorphism, mitotic activity, vascular thrombosis, microvascular proliferation and necrosis.2,4
Grading of CNS tumors
The World Health Organization (WHO) grading of central nervous system (CNS) tumors is based on histologic features of the tumor. Characteristics pertaining to grades I to IV are described here.2
Grade II: Low-Grade astrocytoma (pilomyxoid astrocytoma)
Pilomyxoid astrocytoma is characterized as a slow-growing tumor with indistinct borders that primarily manifests in the hypothalamic region and rarely spreads to other parts of the CNS.2 This tumor is common among the very young, but can occur in older children as well.
Grade IV: Gliosarcoma
Gliosarcoma has a biphasic tissue pattern with glial and mesenchymal differentiation. It commonly affects men between the ages of 40 and 60 years and is located in the cerebral hemispheres.2
Gliomas are the most common form of brain tumors, which begin in the glial (supportive) tissue. Different types of gliomas include astrocytomas, brain stem gliomas, ependymomas, and oligodendrogliomas.1
Based on the World Health Organization Grading System, grade I lesions generally have low proliferative potential with the possibility of a cure after surgical resection. Grade II lesions can be infiltrative, but have low proliferative potential. Despite the low proliferative potential, grade II lesions have to chance to recur and progress to higher grades of malignancy.
Grade III lesions have histologic evidence of malignancy (nuclear atypia and increased mitotic activity). In comparison, grade IV lesions have histologic evidence of malignancy, are mitotically active, prone to necrosis, and can be associated with rapid preoperative and postoperative disease progression and fatal outcomes.2
An astrocytoma may grow anywhere in the brain or spinal cord, but in adults, most occur in the cerebrum; in children, the brain stem, cerebrum, and cerebellum are more common sites for development of an astrocytoma.2 Treatment for astrocytomas is dependent on the grade and location of the tumor. Surgery is the standard treatment for a grade I and II astrocytoma.
Grade II tumors may have additional treatment options depending on the tumor’s location and degree of progression.4 Grade III astrocytomas have the tendency to progress to glioblastoma (grade IV), which causes treatments to be more aggressive and dependent on location and progression.2-4 Grade IV astrocytomas, such as glioblastoma multiforme, can develop directly or evolve from lower grade astrocytoma or oligodendroglioma. The median survival rate is about 15 months.