B7-058 Brain Tumors 2 Flashcards
adult-type diffuse gliomas [3]
astrocytoma
oilgodendroglioma
glioblastoma
you can only grade CNS tumors using
and you should write out what when assigning grade?
arabic numerals 1, 2, 3, 4
“CNS WHO Grade”
most important first step in grading gliomas is determining […] type
IDH
lower grade and better prognosis gliomas have […]
IDH mutations
vast majority of IDH mutations in gliomas will have a point mutation at
R132H
gene encoding cytosolic nicotinamide adenine dinucleotide phosphate-dependent isocitrate dehydrogenase
IDH
IDH mutation in diffuse glioma is associated with [better/worse] prognosis
better
IDH mutations in diffuse gliomas are associated with […] age of onset
younger
how do we test for IDH mutations?
immunostain for IDH1-R132H
(most common mutation)
If immunostain for IDH1-R132H is negative but diffuse glioma is strongly suspected, what is the next best test?
Next Generation Sequencing (NGS)
discovers “non-canonical” IDH mutations
Next Generation Sequencing (NGS)
(mutations other than R132H)
IDH immunostain takes […] days, NGS takes […] days
1-2
10-14
(cannot continue work up until IDH status is known)
high incidence in diffuse astrocytomas
lower incidence in oligodendrogliomas, oligoastrocytomas, and glioblastomas
ATRX mutation
[…] expression is mutually exclusive with 1p/19p co-deletions
ATRX
ATRX expression is mutually exclusive with […] co-deletions
1p/19p
if you have a […] mutation you are very likely to have a diffuse astrocytoma
if you do not, you are very unlikely to have diffuse astrocytoma
ATXR
when IDH mutation is present, the immunostain is […]
positive (tissue turns brown)
when ATRX mutation is present, the immunostain is […]
negative (loose stain)
interpret the result of this ATRX immunostain
not mutated
retained expression
interpret the result of this ATRX immunostain
mutated
loss of expression
very likely diffuse astrocytoma
ATRX mutations are associated with IDH mutations and […] mutations
p53
(usually tested for with p53 immunostain, but more conclusively with NGS)
IDH mutant
tp53 mutant
ATRX mutant
molecular signature of […]
diffuse astrocytoma
poor prognostic factor in IDH mutant astrocytomas
homozygous deletion of CDKN2A/B
(automatically makes it CNS WHO grade 4)
presence of […] mutation automatically makes a IDH-mutant astrocytoma CNS WHO grade 4
homozygous deletion of CDKN2A/B
how to test for deletion of CDKN2A/B? [3]
NGS
FISH
CMA (what KU uses)
a technique used to detect the presence or absence of specific gene sequences
FISH
used to detect chromosomal alterations
FISH
very expensive, very comprehensive test used to analyze genomic copy number variation that can detect very small deletions and duplications
CMA
(basically the entire genome)
turn around time for CMA
14 days
essential for both grade and prognosis of diffuse astrocytoma
CMA for CDKN2A/B
what mutations are required for diagnosis of oligodendrogliomas? [2]
IDH mutations
1p/19p co-deletions
tests for 1p/19p co-deletions [2]
FISH
CMA if FISH doesnt pick it up
IDH mutation
1p/19p co-deletions
molecular signature of […]
oligodendroglioma
molecular signatures of IDH wildtype gliomas [3]
EGFR amplification
whole chromosome 7 gain and 10 loss (+7/-10)
TERT promoter mutation
(only need 1 to classify as WHO grade 4)
[…] confers a better prognosis for IDH wildtype gliomas
MGMT methylation
MGMT is associated with long survival in patients treated with […]
alkylating agents (temozolomide)
why is MGMT methylation considered a good prognostic indicator for IDH wildtype gliomas?
silences the gene so there is no DNA repair
so, the tumor cells are more sensitive to DNA damage from alkylating agents
how do you test for MGMT methylation?
PCR analysis
are CNS gliomas staged?
no
grade
first step in molecular classification of gliomas
IDH status