00:01
So after the imaging evaluation,
we need to figure out,
what is this tumor?
And definitively
diagnose it with tissue,
and begin the
treatment process.
00:09
And the mainstay of those two goals
is really surgery.
00:13
So let's talk more about the
types of surgery that we use,
and why we use those
for gliomas?
Well, the goals of surgery
are number one
to establish a diagnosis.
00:23
Imaging may give us a
concern about what this is,
and we may be pretty sure,
but ultimately, a definitive
tissue diagnosis is required
to treat and manage that patient
with a suspected glioma.
00:35
The second thing is
we'd like to help the patient.
00:38
And many of these
tumors are large,
and pressing on surrounding
structures of the brain
causing symptoms or seizures.
00:43
And so a second goal of surgery
is to relieve symptoms
of mass effect, edema,
and improve patient symptoms.
00:51
For most cancers,
and a glioma is a type of cancer,
we think about staging.
00:56
And staging makes sense.
00:58
You may have learned
of the TNM scale.
01:01
The tumor size,
the number of nodes,
and the degree
of metastatic disease,
and that helps us evaluate,
to diagnose,
and then to manage patients
who may have a cancer.
01:12
This doesn't work so well
for gliomas,
because size doesn't matter.
01:16
Location matters.
01:18
And really small tumors
in the brainstem
are small in size,
but bad in symptoms.
01:23
The brain does drain,
but there is not
an avid lymph node
or lymph node drainage in the brain
that we can follow
that will guide us into the
degree of invasion of those tumors.
01:33
And brain tumors, gliomas,
don't metastasize.
01:36
So that TNM scale
really doesn't help us.
01:39
Instead, when we're
evaluating gliomas,
we grade those tumors.
01:43
And that requires a pathologist
to definitively and comprehensively
evaluate that tumor
under the microscope.
01:50
Pathologic grading
is based on the cell morphology.
01:53
The appearance of the
tumor cells, on the slide,
and the degree of
aggression or invasion
that is seen in that sample.
02:02
Let's look at some examples
of the histologic slides
for patients with gliomas.
02:07
Here we see an example
of an astrocytoma.
02:10
This tumor is a tumor that may arise
from the astrocytes
the most abundant cells
in the brain.
02:16
And those astrocytes are typically
intermixed around normal neurons,
and in low-grade
astrocytomas,
this appears to look very similar
to normal brain.
02:25
In higher-grade astrocytomas,
we see many cells
packed in together.
02:30
Oligodendrogliomas have a
very classic histologic appearance
that you should know about.
02:36
This is the fried egg
appearance.
02:38
As a result of fixation, when these
oligodendrocytes are fixed,
there is a halo that occurs
around the nucleus.
02:46
So we see a small blue nucleus
and a clear halo
that looks like a fried egg.
02:52
And so oligodendrogliomas
histologically
have a fried egg appearance.
02:57
Ependymomas are often packed
cellular tumors with rosettes.
03:02
So how do we grade those tumors?
When the pathologist is evaluating
the tumor histologically,
how do they assess its grade
or its aggressiveness?
Well, grade I tumors
are not infiltrating.
03:14
They are tumors that sit inside the
brain and displace the normal brain.
03:18
They're well circumscribed.
03:20
And we can see that both
on imaging and histology.
03:23
And there are two important
histologic buzzwords
that I'll have you know about.
03:27
You don't need to know
what causes these
but you do want to associate them
with grade I gliomas in your mind.
03:33
And that's Rosenthal fibers
and these things called
eosinophilic granular bodies.
03:38
There are specific
histologic findings
that suggest a diagnosis
of a grade I glioma.
03:44
What are the types of
grade I gliomas?
Well, one is a
pilocytic astrocytoma.
03:49
And you're going to
associate that in your mind.
03:51
Pilocytic astrocytomas
are grade I gliomas,
and grade I gliomas
the most common
is a pilocytic astrocytoma.
03:58
That's an important example of a
grade I glioma to know.
04:02
There are other types.
04:03
The subependymal giant
cell astrocytoma,
this dysembryoplastic
neuroepithelial tumor or a DNET,
and a ganglioglioma.
04:12
But the one I want you to remember
that grade I glioma
is a pilocytic astrocytoma.
04:19
The grade I tumors
are very different
from grade II, III, and IV gliomas.
These are infiltrating tumors.
04:24
They start in a focus and grow into
an evade into the brain.
04:28
So they're called infiltrating.
04:30
We typically see hypercellular
tumors and nuclear atypia.
04:34
The nuclei don't look right
in these neoplastic cells.
04:39
Some examples of grade II gliomas
are the diffuse infiltrating glioma,
a pleomorphic xanthoastrocytoma,
which is really rare
and I don't need you to remember
that but just know of it.
04:50
And something called
the pilomyxoid astrocytomas.
04:53
But a diffuse infiltrating
low-grade glioma
is going to be our
prototypical grade II glioma
that I'd like you to know.
05:00
What about grade III tumors?
These are also infiltrating gliomas
that are hypercellular.
05:06
There's too many cells
growing into the brain.
05:09
These tumors are actively growing
and we can see that histologically.
05:13
There's increased mitotic activity.
We see actively dividing cells.
05:17
And when that is seen that indicates
that this tumor is a grade III
and is more aggressive.
05:22
There can be elevated
molecular markers of proliferation,
Ki-67 and MIB-1
are proteins that are expressed
in cells that are dividing,
and so increase Ki-67, and MIB-1
tells us that this tumor is growing,
and this is a grade III glioma.
05:39
The example I want you to remember
of a grade III glioma is called
the anaplastic astrocytoma,
or the anaplastic
oligodendroglioma.
05:47
Those are grade III astrocytomas,
or oligodendrogliomas.
05:51
And we know that because
of that active proliferation
that the pathologist sees
under the microscope.
05:56
And the last and maybe the
most important glioma to know
is the grade IV glioma,
which we called glioblastoma.
06:04
Again, this is an infiltrating tumor
that grows into the brain.
06:07
There are too many cells
that do not look correct.
06:09
There's hypercellularity,
and nuclear atypia.
06:12
The cells are actively dividing.
We see mitosis.
06:15
And there are
two histologic features
that are pathognomonic
for glioblastoma.
06:20
Meaning that if you hear of these,
that means it's a glioblastoma.
06:23
And you should know these.
06:24
The first is
vascular proliferation.
06:27
There is excess blood vessels
in these tumors.
06:29
And that's what causes them
to enhance avidly with contrast,
and then something called
pseudopalisading necrosis.
06:36
And what's going on
to cause that finding
is the tumor cells
are rapidly dividing,
faster than blood can be supplied.
06:44
And so there's areas of
cell death or necrosis,
and around the necrosis,
around the cell death
are actively growing
and dividing tumor cells
growing away from those
central hypoxic areas
where the tumor cells can't grow.
06:56
And that's very specific
for this diagnosis of glioblastoma.
07:00
So that's how we think of,
and look at,
and diagnose these tumors,
histologically.