Low-Grade Glioma
Background
Low-grade gliomas (LGGs) account for what % of all primary brain tumors?
~15% of all primary brain tumors are LGGs.
Is there a racial predilection for LGG?
Yes. Whites are more commonly affected than blacks (2:1).
What are the 2 classes of LGGs?
Noninfiltrative (WHO I) and infiltrative (WHO II)
What are the histologic subtypes of LGGs?
Histologic subtypes of LGG:
Grade I: juvenile pilocytic astrocytoma (JPA), subependymal giant cell tumor
Grade II: diffuse (fibrillary, protoplasmic, gemistocytic), pilomyxoid astrocytoma (PMA), pleomorphic xanthoastrocytoma, oligodendroglioma, oligoastrocytoma
What 4 pathologic features determine glioma grading?
Necrosis
Atypia
Mitotic figures
Endothelial proliferation
(Mnemonic: NAME or AMEN)
Which subtype of grade II glioma has the worst prognosis?
The gemistocytic subtype tends to de-differentiate and has the worst prognosis. Some prefer to treat it like a high-grade glioma.
Where does JPA most commonly present?
JPA most commonly presents in the posterior fossa (80% cerebellar, 20% supratentorial).
What pathologic feature is characteristic of JPA?
Rosenthal fibers are characteristic of JPA.
Where do grade II LGGs most commonly present?
Grade II LGGs most commonly present in the supratentorium.
What is the median age of Dx for JPA vs. other LGG?
The median age for JPA is 10–20 yrs and for grade II LGG is 30–40 yrs.
What genetic change is an important prognostic factor in LGG?
In LGG, p53 mutation is an important prognostic factor (poorer survival and time to malignant transformation).
What is the natural Hx of PMA?
PMA tends to occur in infants (10−18 mos), mostly in chiasmatic-hypothalamic regions. It is an atypical JPA with a higher rate of CSF dissemination and recurrence.
What genetic change is prognostic in oligodendroglioma?
LOH 1p + 19q (50%−70%) is prognostic in oligodendroglioma.
What is the characteristic pathologic appearance of oligodendroglioma?
“Fried egg” appearance (round cells with nuclear halo) is characteristic of oligodendroglioma.
Where do most oligodendrogliomas occur in the brain?
Most oligodendrogliomas occur in the hemispheres (80%).
Anaplastic transformation from LGG to HGG occurs in what % of pts?
~70%–80% of pts with LGG will undergo anaplastic transformation (based on EORTC 22845).
What is the genetic mutation in NF-1, and with what type of gliomas is it associated?
NF-1 is a result of a mutation on the long arm of chromosome 17 and is associated with optic/intracranial gliomas.
What is the genetic mutation in tuberous sclerosis, and with what glioma is it associated?
Tuberous sclerosis is a result of a mutation on chromosome 9 and is associated with subependymal giant cell astrocytoma.
What syndrome is associated with gliomas and GI polyposis?
Turcot syndrome is associated with gliomas and polyposis.
Can you have mitoses in LGGs?
Yes. If the tumor is small, even a single mitosis upgrades it to at least WHO III (anaplastic). However, if the tumor is large, a single mitosis may not upgrade it to a high-grade histology.
With what Sx do LGGs most commonly present?
Seizures (60%−70%, better prognosis) > HA, focal neurologic Sx
Workup/Staging
What is the workup for suspected glioma?
Suspected glioma workup: H&P, basic labs, and MRI brain
How should tissue be acquired for Dx?
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