Oligodendroglioma
Epidemiology:
Common sites:
Gross features:
Histologic features:
- fine chickenwire vasculature
- uniform cytology
- round, dark nuclei (like a lymphocyte)
- “fried egg” morphology (perinuclear clearing)
- Formalin artifact
- may not see in well-fixed tissue or rapidly
fixed tissue
- not seen in frozen or smears with other
fixative
- very useful if present
- no clear cell borders
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
- loss of 1p and 19q (good response to chemo and
RT, and longer overall survival) (50-90% of oligodendroglioma):
- typically loss of the entire chromosomal arms
- minimally deleted region has not been
determined
- likely reflects the loss of tumour
suppressor gene(s) on one of the chromosomes
- combined loss is rare in gliomas
other than oligodendroglioma
- 20-30 % of mixed oligoastrocytoma
(MOA)
- Low in diffuse gliomas
with ambiguous morphologies in general
- Not seen in small cell astrocytoma
- Not seen in DNET
- note: isolated loss of 19q occurs in frequently
astrocytoma and MOA
- rare in pediatric oligodendrogliomas
(which are also rare)
- inverse association with TP53 mutation, 10q loss,
9p loss, and EGFR amplification
- LOH at 1p or 19q by PCR:
- assessed by loss of heterozygosity assays
using microsatellite markers on 1p (8 loci) and 19q (7 loci)
- must compare tumour
to normal sample (ex peripheral blood)
- multiplex PCR to amplify up each
microsatellite allele
- capillary electrophoresis to detect loss of an
allele (loss of a peak) compared to the normal sample
- unclear whether loss of 1p and 19q predicts
better response to treatments, or whether they are biologically more
indolent
- more likely to present with seizures rather
than focal neurologic deficit
- rarely found:
- 10q deletion (consider diagnosis of
astrocytoma)
Other features:
- 2/3 are very sensitive to chemotherapy
- LOH at 1p and 19q predicts good response
- >= 6 mitoses / HPF may predict a reduced
survival time
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References:
- Aldape K, Burger
PC, Perry A. Clinicopathologic
aspects of 1p/19q loss and the diagnosis of oligodendroglioma. Arch Pathol
Lab Med 2007;131:242-251