Okay. Welcome back.
We've already talked now
about benign versus malignant
and including dysplasia and
how a pathologist and now you,
think about how a cell looks,
in terms of deciding whether
it's malignant or benign.
We're going to go now into further
pathologic evaluation of tumors
and this involves tumor “Grading” and “Staging”
and sometimes these terms are confused,
so, we'll spend a little bit of time
hopefully clarifying it for you.
Tumor grading general principles.
This is what we see looking down the microscope,
it's a microscopic assessment of
various features of the tumor.
The degree of differentiation,
will determine whether something
is a well-differentiated, moderately
differentiated, poorly differentiated tumor
and that will affect the grading.
We look at the number of mitoses,
so, the proliferative index,
we look at whether or not the
mitosis are normal or abnormal,
we evaluate for necrosis and
we evaluate histologically,
for vascular lymphatic
perineural or capsular invasion
and all of those things will
affect the grade of the tumor,
from a high grade tumor which tends to do worse
or a low grade tumor which tends to do better
and the more abnormalities we have
typically the higher the grading.
Just as an example here, this is
showing a differentiation pathway
that's used to determine
whether a prostate cancer,
is well differentiated at the top,
versus very poorly differentiated
or anaplastic at the bottom
and the general features that you
see in terms of the organization,
whether you have small uniform glands
or you have infiltrative margins,
whether you have poorly organized glands
or whether the cells are
just looking totally bizarre,
will go from a well-differentiated
low-grade tumor at the top,
to a poorly differentiated
high-grade tumor at the bottom.
And there are similar sorts of
organization and grading schema
they're used for every different cancer,
this just happens to be the
one used for prostate cancer.
So, what does this mean in
terms of looking at a tumor?
Well, the tumor on the left,
is a low-grade leiomyosarcoma,
it's a malignant tumor, most
of the cells that are in there,
look kind of like smooth muscle cells.
On the right-hand side is one
that's poorly differentiated,
looking at that, I don't see
any of those spindly cells,
that I see on the left-hand side.
It looks like I just have bizarre
things that are all over the place,
including wild mutations.
That cell at the very top,
with kind of pentapolar
mutation or pentapolar mitosis.
So, one is well differentiated
and will tend to do better,
not be as aggressive,
versus the poorly differentiated
tumors, that tend to do worse.
So, when we look through the microscope,
here's another example of
Well differentiated, the glands are
nicely formed there are lots of them
and it's recognizable as glandular epithelium.
As it gets a little bit less well differentiated,
it gets more hyperplastic,
the glands are still there,
but they tend to be smaller
and not as well formed.
And finally in poorly
differentiated adenocarcinoma colon,
oh my goodness, it's almost impossible
to see any glandular differentiation,
the tumor has acquired so many mutations,
that it totally doesn't care
that it was supposed to start out
life as a colon epithelial cell
and now, I just have proliferating cells in nests
and bundles throughout the tissue.
As part of our histologic
evaluation, in terms of grading,
we will also see whether tumors have
other things that they are making.
So, if they're making lots of mucin,
all that kind of clear gray stuff,
inside of the cells, or whether
they're forming a distinct appearance,
so-called signet ring cell, where you
have nuclei at the edge of the cell,
around a collection of mucus
within each individual cell,
so, it looks like a signet ring,
that you would wear from
your fraternity for example.
Those all will have impact,
whether it's well differentiated,
poorly differentiated or making
mucin, making signet ring cells,
all of that will affect the
tumor grade and as I said,
it's different in terms of the parameters
that we look at for every tumor.
So, in Gleason grading for the prostate,
we don't have mucinous or signet ring cells,
we just have well differentiated,
moderately and poorly.
So, in colon cancer we do.
I don't expect you to remember those distinctions,
but be aware that, when you
become world famous oncologist,
pay attention what your
pathologist is telling you,
in terms of the degree of
differentiation other features.