Brain tumor grading

The grading of brain tumors intends to provide a general estimate of a lesion's anticipated biologic behavior. In brain tumor pathology a four-tiered grading system is usually used. Grade I indicates postoperative cure or at least a survival time of 5 or more years. Grade II corresponds to a postoperative survival time of 3 to 5 years. Grade III corresponds to a mean survival of 2 to 3 years after "total" resection and grade IV has a short survival time of about 6 to 18 months. The histological assessment of the grade of the tumor is based on the following criteria: nuclear atypia, mitotic activity, endothelial proliferation, necrosis and cellularity. It is noteworthy that these histologic variables should be interpreted in relation to the tumor type. In pilocytic astrocytoma, for example, endothelial proliferation is not associated with more malignant behavior, but the same feature is a bad prognostic sign in diffuse astrocytoma. Hence, tumor type is per se an important indicator of biologic behavior as well.

Astrocytic tumors

Subependymal giant cell: Grade I

Pilocytic: Grade I

Low grade: Grade II

Pleomorphic xanthoastrocytoma: Grade II, Grade III

Anaplastic: Grade III

Glioblastoma: Grade IV

Oligodendrogliomas

Low grade: Grade II

Anaplastic: Grade III

Oligo-astrocytomas

Low grade: Grade II

Anaplastic: Grade III

Ependymal tumors

Subependymoma: Grade I

Myxopapillary: Grade I

Low grade: Grade II

Anaplastic: Grade III

Choroid plexus tumors

Papilloma: Grade I

Carcinoma: Grade III, Grade IV

Neuronal/glial tumors

Gangliocytoma: Grade I

Ganglioglioma: Grade I, Grade II

Desmoplastic infantile ganglioglioma: Grade I

Dysembryoplastic neuroepithelial tumor: Grade I

Central neurocytoma: Grade I

Pineal tumors

Pineocytoma: Grade II

Pineocytoma/pineoblastoma: Grade III, Grade IV

Pineoblastoma: Grade IV

Embryonal tumors

Medulloblastoma: Grade IV

Other PNETs: Grade IV

Medulloepithelioma: Grade IV

Neuroblastoma: Grade IV

Ependymoblastoma: Grade IV

Cranial & spinal nerve tumors

Schwannoma: Grade I

Malignant peripheral nerve sheath tumor: Grade III, Grade IV

Meningeal tumors

Meningioma: Grade I

Atypical meningioma: Grade II

Papillary meningioma: Grade II, : Grade III

Hemangiopericytoma: Grade II, : Grade III

Anaplastic meningioma: Grade III

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