CNS & pituitary tumors
Gliomas, glioneuronal tumors, and neuronal tumors
Glioma overview
Author: Eman Abdelzaher, M.D., Ph.D.
Last author update: 1 March 2012
Last staff update: 15 May 2023 (update in progress)
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: Glioma [title] CNS [title]
Table of Contents
Definition / general | Terminology | Clinical features | Classification | Microscopic (histologic) description | Positive stains | Negative stains | Differential diagnosisCite this page: Abdelzaher E. Glioma overview. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/cnstumorgliomageneral.html. Accessed June 7th, 2023.
Definition / general
- Most common CNS tumor
- Includes astrocytoma, ependymoma, glioblastoma, oligodendroglioma and various subtypes / combinations
- Diagnosis of "glioma" may be used for frozen section but is not a final diagnosis
- Important to identify oligodendroglial component, due to effectiveness of chemotherapy for these gliomas
- Presence of thrombosed vessels in tumors may predict postoperative systemic thromboses (J Neurosurg 1998;89:200)
- The etiology of gliomas is not entirely understood, but a known risk factor is radiation therapy to the cranium, and gliomas in this setting usually arise 5-25 years after exposure
Terminology
- Intra-axial: within brain and spinal cord
- Intramedullary: within spinal cord
- Extra-axial: not within brain and spinal cord (such as meningioma)
- Extramedullary: not within spinal cord
- Supratentorial: above tentorial membrane - cerebrum
- Infratentorial: below tentorial membrane - cerebellum, brainstem or spinal cord
Clinical features
- 13K deaths in US annually (2% of cancer deaths)
- Peaks in childhood, then declines to age 25 years, then increases with age
- Childhood tumors: 33% in anterior fossa (supratentorial), 67% in posterior fossa (astrocytoma - 26%, medulloblastoma / PNET - 24%, ependymoma - 14%)
- Adults: metastases are more common than primary brain tumors but are usually not biopsied; of biopsied tumors, 67% arise in anterior fossa (glioma - 33%, meningioma - 13%, metastases - 12%, pituitary adenoma - 5%), 33% in posterior fossa (schwannoma - 8%, misc. - 33%)
- Most common spinal cord tumors are schwannoma, meningioma and ependymoma
- Metastasis of primary CNS tumors outside CNS is rare, usually occurs along brain and spinal cord via subarachnoid space or due to surgery related implantation of tumor cells into vessels
- Benign appearing tumors may still be infiltrative and difficult to resect
- Tumors may arise from neural stem cells, precursors of neurons and glial cells, recently discovered in mature brain
- Symptoms: focal deficits, seizures, increased intracranial pressure (due to mass effect, hydrocephalus, cerebral edema), herniation
- Labeling index / proliferation index: percentage of MIB1+ or PCNA+ nuclei (compared to all nuclei), usually in regions of highest proliferation; useful prognostic indicator (high values associated with poorer prognosis)
Classification
- Benign: does not recur; applies to pilocytic astrocytomas, certain gangliogliomas and ependymomas; may still have poor prognosis due to location that makes it difficult to resect completely
- Low grade: may recur as high grade and kill patient
- Gliomatosis cerebri: diffuse and extensive involvement of CNS associated rarely with glioma; MRI and biopsy helpful for diagnosis
Microscopic (histologic) description
- Biopsies of tumor epicenter have cellularity greater than surrounding brain
- Biopsies of margin only are difficult to grade; often contain granular calcifications among hypercellular glia
- Also microcysts and mitotic figures (depending on tumor grade)
- May have uneven distribution of cellular density that obscures gray white junction or spawns secondary structures of Scherer (subpial and perineuronal neoplastic glia)
Positive stains
Negative stains
- Collagen, reticulin, fibronectin
Differential diagnosis
- Gliosis: even distribution of cellular density, contracts instead of expanding near hypercellular glia; usually less pleomorphism, no nuclear hyperchromasia, no nuclear cluster formation, no nuclear molding, no mitotic figures, no calcifications
